Iran financed the confinement and upkeep of the American hostages who were held in Lebanon and also paid their captors $1 million to $2 million for each hostage released, according to Bush administration officials who have studied the long ordeal and eventual liberation of the captive Americans.

U.S. officials interviewed since last month's release of Terry Anderson, the last of the American hostages, said nearly all the key negotiations about the American captives were in Tehran, rather than Lebanon, and advance word of impending releases came from the Iranian Foreign Ministry through diplomatic channels several days ahead of each recent release. The officials said Lebanese fundamentalists who directed the incarceration of the hostages were provided with Iranian travel documents and conferred frequently with Iranian diplomats.

Moreover, officials said regular money payments to the groups holding the Americans and other Western hostages were traced by U.S. intelligence to official Iranian sources. The $1 million to $2 million paid to the hostage-holders in connection with each release was in addition to the regular payments and was described by one official as a "per capita" award for hostage termination.

Asked why Iran had to pay the captors for the releases if it exerted overall control anyway, a senior U.S. official said the Iranians "want to keep these people happy, quiet and on their side. They have long-term investments in Lebanon. They are there for the long haul." Officials declined to give details of Iran's financial involvement with the hostage-keepers because they said the information is based on highly classified intelligence reports.

"The road to the hostages ran through Tehran," said an administration official who for the past six years led a U.S. unit that concentrated on the long-running issue. He and others expressed the belief that the holding of American hostages in Lebanon was terminated not because of inducements or deals, as was attempted during the Reagan administration, but because the hostages had outlived any possible usefulness with the passage of time, the realignment of East-West relations and the unwillingness of Washington to bargain.

These officials said Iran concluded that the continued captivity of the hostages was a serious detriment to the Islamic republic's efforts to win economic access to the West at a time when the Soviet alternative had collapsed. The hostages also had become more of a burden than an asset to the fundamentalist Shiite groups in Lebanon who seized and held them for years.

Iranian officials had often tied their cooperation in obtaining the release of the hostages in Lebanon to the return of Iranian assets impounded by the United States in an earlier hostage episode -- the 1979 seizure of the U.S. Embassy in Tehran. The Bush administration, recognizing Iran's interest, shifted gears in 1989 to speed action in the U.S.-Iran Claims Tribunal at The Hague. In a much-noted action Nov. 29, amid the final releases of U.S. hostages, the United States announced payment of $278 million in compensation for seized Iranian military equipment. However, U.S. officials have provided an account of U.S.-Iran negotiations showing that the coincidence of timing was due to Tehran, not Washington.

While Americans were still being held in chains in Lebanon, Washington officials had been willing to discuss Iran's behind-the-scenes role only in the most guarded terms. In recent weeks, officials disclosed new details and assessments of the Iran connection, some of which were based on developments in the endgame negotiations.

"Iran had a substantial amount of authority in almost all cases," said a senior U.S. official with access to the complete file on the hostages. Another senior official said, "We used to spend endless hours debating here the degree of Iranian control. The evidence now is that control was 99.9 percent."

A third senior official who carefully studied all information about the hostages said Iranian control over the hostages may have been less clear-cut than the others believe. He said Iran had "about as much control as you do over your 16-year-old son," which is to say the levers of power are there to be used but the realistic question is, "How much pressure are you willing to bring to the table?"

Iran's ambassador to the United Nations, Kamal Kharrazi -- one of a dozen high-ranking diplomats and officials interviewed in Washington and the United Nations for this article -- said reports that Iran had control over the captive Americans and other Western hostages in Lebanon were "baseless."

"Those who have such imaginations don't understand Lebanon, the Lebanese people and these {hostage-holding} groups," the ambassador added. If there was an Iranian influence, Kharrazi said, it was "spiritual influence," which was exerted through "different channels of communication" to encourage Lebanese groups to release their hostages. Kharrazi said that, to his knowledge, money was not a factor in either the seizure or release of the hostages. Iran's Early Role Clouded

Iran's role in the original capture of American and other Western hostages in Lebanon is obscure. But experts said the seizure of the U.S. Embassy in Tehran in November 1979, and the holding of U.S. diplomats for 444 days at the end of the Carter administration, convinced some Iranian factions as well as their sympathizers in Lebanon that hostage-holding was an effective form of revolutionary warfare, with an impressive political payoff as well as potential economic gain.

In Lebanon, the hostage-takers were identified by U.S. officials as clandestine elements of Hezbollah, an umbrella organization of Lebanese Shiites that is inspired and aided by Iran and which also has religious, social and political functions.

Some former hostages have reported being held near Iranian forces. The Rev. Lawrence Jenco said his guards sometimes brought him food from a nearby Iranian Revolutionary Guards camp. Frank Reed said that from one of his places of captivity, he could see Iranian Revolutionary Guards marching nearby.

One of the most prominent of the Lebanese hostage-holders, Imad Mugniyah, met regularly with Iranian diplomats in Beirut, Damascus and Tehran, according to a U.S. official. In a recent book, former hostage David Jacobsen, who met him several times while in captivity, called Mugniyah "the boss of all bosses in the hostage operations."

Another important governmental player was Syria, which held military sway over much of Lebanon and therefore was in a position to pressure the hostage-holders. Although Syrian intelligence conceded it knew at times where the hostages were, officials in Damascus indicated to then U.S. Ambassador Edward P. Djerejian that they were reluctant to stage a raid because hostages could be killed. Syria was often allied with Iran against Iraq, but Syrian authorities took an increasingly dim view of the holding of Western hostages as they sought improved Western relationships in the post-Cold War era.

The first American to be kidnapped and held in Lebanon, David S. Dodge, acting president of American University of Beirut, was seized by Lebanese militants in July 1982 and taken to Iran for questioning before his release after a year in captivity. Dodge's kidnapping came amid a rise in anti-Americanism following Israel's invasion of Lebanon and likely was in response to the disappearance two weeks earlier of four Iranians -- two diplomats, a journalist and their driver. The four are now believed to have been killed by a Lebanese Christian militia.

A key figure in the wave of kidnappings that began in early 1984 was Mugniyah, a charismatic young Lebanese Shiite who was chief bodyguard for Hezbollah leaders. Officials suspect Mugniyah's hostage-taking was initially devised as a pressure tactic against the Western-backed government of Kuwait, which sentenced Mugniyah's brother-in-law and several other terrorists to death for car-bomb attacks in December 1983 against U.S. and French embassies and other targets in Kuwait that killed five people.

The emir of Kuwait subsequently commuted the death sentences but steadfastly refused to release the prisoners, who were associated with an Iranian-backed movement, Al Dawa (The Call).

Mugniyah participated in, and may have planned, the hijacking in June 1985 of TWA Flight 847, the first high-visibility hostage episode of the Reagan administration. After most of the passengers were released, a small group kept behind by Mugniyah was let go only after personal intervention by Ali Akbar Hashemi Rafsanjani, then speaker of the parliament and now president of Iran. This demonstration of Iran's influence with the Hezbollah captors was the starting point of the secret U.S. efforts in 1985-86 to negotiate with Iran for the release of the Americans being held in Lebanon, according to anti-terrorist officials who were in government at the time.

Following the eruption of the Iran-contra scandal, the United States reverted to a "no concessions" stand regarding hostages. At the same time, in indirect dialogue through Swiss ambassadors in Washington and Tehran, the United States said repeatedly since 1987 that it was ready for an authoritative, face-to-face discussion with an authorized Iranian representative.

"Sometimes they seemed willing to entertain it, other times not," said a U.S. official who has monitored the communications. "But always they said that they would expect and need confidentiality, and that if meetings were held, they be secret."

On two or three occasions, this official said, the two sides exchanged views about opening direct U.S.-Iranian talks, and there were preliminary exchanges on "at least a rough agenda," with Washington insisting that the hostages and state-sponsored terrorism top its list. At one point in 1990, it was nearly decided that Undersecretary of State Robert M. Kimmitt would open the talks with an Iranian deputy foreign minister at the United Nations. However, Iran's demand for complete secrecy posed an insurmountable obstacle. Bush's Conciliatory Posture

From the beginning of the Bush administration, the United States adopted a more conciliatory overall position regarding Iran while still refusing to negotiate about hostages. In his inaugural address, President Bush went out of his way to refer to the hostages and to say, with no specific mention of Iran, that "assistance can be shown here and will be long remembered. Goodwill begets goodwill."

The Reagan administration, traumatized by the public reaction to its secret arms-for-hostages dealings with Tehran, had been reluctant to continue the litigation at the U.S.-Iran Claims Tribunal set up in 1981 to settle the financial claims of the two nations. After hearing Bush's inaugural speech, Abraham D. Sofaer, then State Department legal adviser, recommended that he be authorized to proceed with all deliberate speed in negotiations at The Hague. Sofaer said this was approved by his superiors, all the way up to Bush, and that "there was no doubt whatsoever that what we were doing {at the tribunal} was helping to aid Iran in the release of the hostages" because Tehran persistently related the hostages to the claims issue. However, from the U.S. standpoint, Sofaer said, "we were doing what was entirely proper and what we were obligated to do under international law" by settling the Iran claims on a fair and legally correct basis.

Questions were raised throughout the claims settlement process about the relationship with hostage releases, particularly when a $278 million award to Iran, which had been four years in the making as compensation for seized Iranian military equipment, was approved last Nov. 29 amid the final hostage releases. Both Sofaer and his successor as State Department legal adviser, Edwin D. Williamson, said in interviews there was no quid pro quo for hostages involved in negotiating this large Iranian claim.

At the request of The Washington Post, Williamson furnished a chronology and explanation of U.S.-Iranian negotiations on this claim since 1988. These records show the United States agreed to pay Iran the $278 million in a meeting between Williamson and the chief Iranian negotiator, Goudarz Eftekhar-Jahromi, at The Hague last Feb. 14-15, but the payment was delayed by Iran's refusal in four more rounds of negotiations -- on Mar. 28-29, June 5-6, July 29-30 and Oct. 7-8 -- to accept the U.S. demand that some of the money be used to replenish an Iranian account from which U.S. claims are paid. Finally in November, said Williamson, Iran notified the United States "fairly abruptly" that it would accept the U.S. position, clearing the way for the long-pending award.

The slow evolution in Iran's thinking about the hostage issue was influenced by the end of the eight-year Iran-Iraq War in mid-1988, the death of Iran's radical national leader, Ayatollah Ruhollah Khomeini, in mid-1989 and the election of Rafsanjani as Iran's president shortly thereafter. As Rafsanjani consolidated his power, shutting out more radical clerics who sponsored terrorism in Lebanon, the economic crisis in Iran was deepening. Largely due to its perceived complicity in the holding of U.S. and other Western hostages, Iran was isolated from the West and cut off from assistance from the World Bank as well as from many commercial financial institutions.

Washington's position, according to Thomas R. Pickering, the U.S. ambassador to the United Nations who transmitted it several times to Tehran through U.N. channels, was that the Iranians "were being held hostage themselves by the hostages, rather than the other way around, that these people had become an enormous liability, that they stood in the way of any opportunity the Iranians had of opening themselves to a wider field." Pickering said reports received through the United Nations indicated the message was getting through.

The clearest sign of a shift began with a February 1990 Rafsanjani meeting in Tehran with leaders of Hezbollah. On the next day, in a speech to the Iranian parliament, Rafsanjani expressed concern that recent revolutions in Eastern Europe and U.S.-Soviet reconciliation would make Iran more vulnerable to outside powers such as the United States. A few days later, the pro-government Tehran Times, in an editorial rumored to have been written by Rafsanjani, called on "all active forces in Lebanon" to work to free "all hostages" and suggested that the hostage issue, whatever its origin, was hurting Iran. Break in the Hostage Crisis

Two months later, in April 1990, Washington policymakers were surprised to receive word from the Iranian Foreign Ministry through the Swiss Embassy channel that two American hostages -- the first to be released since the Iran-contra dealings -- would be freed within a few days. On April 22, Robert Polhill, an American University of Beirut business professor, was released, followed on April 30 by educator Frank Reed. Both were in poor health.

There were hopes in Washington that the freeing of Polhill and Reed without preconditions or payoffs would lead quickly to release of the six other Americans being held. However, the United States was informed through the Swiss channel that Iran "expected something" for turning loose the two hostages. "They wanted a gesture {such as} nice words from Bush, perhaps more than money. They wanted a signal from Bush that all would be well," said a U.S. official. "They wanted a subtle price, a hidden price," said another American policymaker.

Privately, indirect contacts continued through the Swiss, with messages being exchanged once or twice monthly in this period, according to a senior State Department official privy to the communications. In order not to appear too eager, the United States rarely initiated an exchange of communications. But when receiving a message from Tehran, "we always responded promptly, politely and directly," said this official.

In August 1990, Iraqi President Saddam Hussein sent his forces into Kuwait and the war that followed in early 1991 "was the single most dramatic political and military event" that led to release of the hostages, according to a White House official who followed the developments closely.

The early hours of the Iraqi invasion brought the escape from a Kuwaiti prison of the 15 Dawa terrorists (two others had already served their time and been released). Mustafa Youssef Badreddin, the brother-in-law of Mugniyah, made his way to Iran and then back to Lebanon, where he was reported to have been installed on a Hezbollah council.

With the United States taking the lead in evicting Iraqi forces from Kuwait, Washington and Tehran had common cause and urgent need for coordination. Messages flew back and forth on an almost daily basis during the military buildup and war in the Persian Gulf. When U.S. officials had anything to say publicly about Iran, it was mostly neutral or even positive.

Early last year, word began to reach Washington from Iranian authorities through the Swiss that they were ready to try to bring the entire hostage-holding episode to a close. Swiss Foreign Minister Rene Felber flew to Tehran in early April in an effort to arrange a "package deal" that would bring about a general release of all captives held without trial in the Middle East.

This would have involved, in addition to American, British and German hostages in Lebanon, release of Lebanese Shiites held by Israel and the bodies or remains of Israeli soldiers who had been lost in Lebanon. By June, the Swiss effort had become deadlocked on the issue of the missing Israelis, with Iran and its Lebanese allies being unable or unwilling to produce them.

Starting in February and March, U.N. Secretary General Javier Perez de Cuellar had extensive contacts with Kharrazi, Iran's U.N. envoy, and Foreign Minister Ali Akbar Velayati to seek a solution to the hostage issue. By mid-summer, after the Swiss efforts had been stymied, Perez de Cuellar devised a U.N. plan for comprehensive releases involving all Western and non-Western hostages in the Middle East. The Iranians showed great interest.

Perez de Cuellar also kept in close touch with the Bush administration through telephone calls and some confidential meetings with national security adviser Brent Scowcroft. Both Perez de Cuellar and a spokesman for Scowcroft said no deals were involved, only exchange of information.

A European diplomat close to the hostage negotiations said the United Nations was chosen for the key role in the release of the American and British hostages because the Iranians trusted Perez de Cuellar and because "they concluded that the only payment they could get {for releasing the hostages} was something on the Iran-Iraq War from the U.N. secretary general."

Acting under the authority of Security Council Resolution 598, Perez de Cuellar last year dispatched two U.N. missions to Iran to assess war damage done by Iraq. On Dec. 9, shortly after release of the last U.S. and British hostages, the U.N. secretary general issued a formal report finding that Iraq was responsible for starting the Iran-Iraq War. Perez de Cuellar denied these actions were hostage-related, but many U.S. officials believe otherwise.

Last August, what would be the final round of hostage releases got underway with the release of British journalist John McCarthy and American author and book salesman Edward Tracy. As in the previous releases in the spring of 1990, the administration was notified several days in advance by the Iranian Foreign Ministry through the Swiss that an American was to be freed. McCarthy brought out a letter signed by Islamic Jihad and addressed to Perez de Cuellar, promising to release the remaining Western hostages if the U.N. chief could arrange the release of all Muslim "freedom fighters" in the Mideast and Europe. The letter officially put the negotiations in the U.N. court; from then on, advance word of hostage releases came to Washington through U.N. channels as Perez de Cuellar's personal assistant, Giandomenico Picco, was alerted to be on hand in Damascus for the events.

Picco met in remote spots in Lebanon with the captors of the hostages a dozen or more times in all, always alone and at night. Asked why he felt his efforts would be fruitful while those of Anglican church envoy Terry Waite had ended with his own captivity, Picco replied: "We discovered if you want to solve {the problem of} the hostages, you don't start in Beirut. Beirut is the last stop. . . . That was the landing site for me, not the takeoff site."

A senior U.S. official, while praising Picco's bravery, said the hostages had been freed for Iran's own reasons and characterized the U.N. activity as only "the most convenient mechanism" for making the arrangements.

In the end, the U.N. efforts to bring about a general swap of Western, Lebanese and Israeli hostages foundered once again on failure to produce the missing Israelis. Nevertheless, the last three Americans -- Joseph Cicippio, Alann Steen and Terry Anderson -- were finally freed in early December.

Staff writers Nora Boustany, Dana Priest and Valerie Strauss contributed to this report.