Late in 1982, as Edgar Chamorro recalls it, an authoritative sounding CIA official told him the Reagan administration had decided to help Nicaraguan exiles overthrow the Sandinista government.

"I remember he said he was speaking on behalf of the president of the United States, who was very interested in getting rid of the Sandinistas," Chamorro said in a review of his two years as a top leader of the U.S.-backed Nicaraguan insurgency.

The official, who introduced himself as "Tony," had flown down from Washington to hold the meeting with Chamorro and similar sessions with other prospective rebel chiefs in a hotel suite overlooking Biscayne Bay, Chamorro said, and he was telling the determined exiles exactly what they wanted to hear about U.S. policy toward their homeland.

Chamorro's recollections of pledges of support for overthrowing the Nicraguan government are contested by some of his colleagues but corroborated by others. Still others avoided the issue.

The version given by Chamorro, after he was dismissed last week from the rebel movement's top leadership, constitutes one man's version of an exercise in ambiguity: U.S. policy in support of anti-Sandinista rebels. Over the past two years, according to congressional testimony, administration officials and rebel leaders, the policy has been like a mirrored ball: radiating definitions and goals that are shaped by and for the angle of the participants.

"I can imagine they would tell them what they thought was necessary to get them mobilized," an administration official said of the CIA briefings to the rebels, which he said explained U.S. objectives and the "distinctions of motivations" that existed between the CIA and the rebels committed to overthrowing the Managua government.

Congress soon will have to try again to decide what U.S. objectives should be and whether they merit renewal of the U.S. funding cut off last spring. Those involved expect the Reagan administration, armed with its triumph at the polls, to make a concerted effort to keep the anti-Sandinista rebellion going by reviving CIA financing.

Congress refused new funding in February. The rebels have said the CIA pipeline ran dry in June but has been refueled by almost $3 million raised elsewhere.

Congress and the American public were given a variety of explanations for the covert war as circumstances changed, but they were never told what Chamorro says he was told -- that the aim of the operation all along had been to topple the Sandinistas by force.

When the administration originally went to Congress for funds in December 1981, the policy was described as a campaign to interdict arms supplies from the Sandinista government to Salvadoran guerrillas, according to a report in May 1983 from the House Permanent Select Committee on Intelligence.

But "interdict" had a wider meaning than simply seizing arms shipments, the report said. The idea also was to show the Sandinistas that their attempts to promote subversion in El Salvador would be met by subversion at home.

"The end purpose of this support has been stated to be the interdiction of arms flowing through Nicaragua into El Salvador," the report said in a review of the program's history. It has also been explained as an attempt to force the Sandinistas to turn away from support of the Salvadoran insurgency.

An administration source explained that Congress was given a description of the interdiction campaign in both its meanings from the start of CIA support for the rebels.

"From the beginning, we had seen it [the insurgency] as a counterpoint for Nicaragua's actions, to make them cease and desist," an administration source explained. He added, "It would have defied logic for anyone to think that the sole purpose of an anti-Sandinista program was to intercept arms traveling down a trail."

But the report said the administration also supplied a third level of meaning to Congress. In this definition, the insurgents would not only prevent something -- arms shipments -- they also would produce something -- increased willingness within Nicaragua to meet U.S. demands for regional talks and democratization. "Later, other goals -- 'bringing the Sandinistas to the bargaining table and forcing the scheduling of promised elections' -- were added as ends to be achieved," the report said.

But one definition the program was not supposed to have was overthrowing the Nicaraguan government. The then secret fiscal 1983 intelligence authorization budget bill contained a congressional restriction in its classified annex barring use of the money "to overthrow the government of Nicaragua or provoke a military exchange between Nicaragua and Honduras." The prohibition, first attached when the authorization was voted in secret in April 1982, became public as the Boland amendment in December that year. According to Chamorro, it was about six months after the secret prohibition, and just before the amendment of Rep Edward P. Boland (D-Mass.) was made law, that the self-assured CIA official on a visit to Miami was making promises of U.S. assistance to overthrow the Sandinista government.

"I believed him because he was using such strong words, the U.S. government, that the president was interested in getting rid of the Sandinistas," Chamorro recalled.

He added that the man known as Tony, which Chamorro said was a pseudonym, also urged swift action, explaining that the administration would be forced to ease off in 1984 because of electoral concerns.

Chamorro said no one else was present at the meeting, and other leaders in the rebel movement asserted that they had never met an official using the full pseudonym that Chamorro supplied.

When rebel attacks in northern Nicaragua produced little in the first half of 1983, Chamorro said, a high-ranking CIA official visited insurgent headquarters in Tegucigalpa, Honduras, in October and urged the irregulars to capture and hold some territory on which to set up a provisional government.

"At that meeting, they came with very strong assurances that the provisional government would be recognized and that they would break relations with the Sandinistas," he declared.

But an administration source said leaders of Chamorro's Nicaraguan Democratic Force, the main rebel group, received lengthy explanations of U.S. policy limitations, including the "distinctions of motivations" between the Reagan administration and the insurgent leaders.

The organization's president, Adolfo Calero, avoided questions on precise meetings with CIA offiicials but he said he understood from the beginning that the rebel goal of overthrowing the Sandinistas was not shared by the CIA and Congress.

"We all knew what we were getting into," he added in an interview. As to whether he also felt deceived by the CIA, Calero cracked: "I would be an ass if I did, and twice an ass if I said so."

Chamorro, educated at Harvard and trained as a Jesuit, should have known better than to take what he was told literally, Calero declared, adding: "He has a lot of experience; how can a 50-year-old man be so grossly misled?"

Calero and others on the movement's seven-member National Directorate expelled Chamorro last Saturday, an action that Chamorro charged was carried out because of CIA anger over his complaints.

Another directorate member, Alfonso Callejas, also said the leadership was aware of congressional restrictions, which he called "the law of the land." But rebel fighting forces are dispatched with the declared objective of overthrowing the government because the guerrilla war is one of several methods being used, he added.

"They [the combatants] are fighting to overthrow the Sandinistas -- that is their goal," he explained. "But our goal is to establish democracy in Nicaragua through various pressures: economic, military, diplomatic and political."

A recently resigned rebel militant objected that he, like Chamorro, was told by CIA advisers that they shared his goal of overthrowing the Nicaraguan government. This is why thousands of young Nicaraguans are putting their lives on the line in the hills of Nicaragua, he said, and this is what they are told by their leaders.

Calero estimated the Nicaraguan Democratic Force, includes about 14,000 armed men, mostly peasant youths disenchanted with five years of government by the Marxist-led Sandinistas.

In part because the insurgent forces expanded to such strength under CIA tutelage, some Democratic congressmen have grown suspicious of administration adherence to provisions of the law barring U.S. funds from being spent to overthrow the Sandinistas.

The suspicions were encouraged by frequent declarations from rebel leaders and action by combatants in Nicaragua, reported in the American press, that depicted an effort openly directed toward overthrow of the Sandinistas. Chamorro, who served as rebel spokesman in Tegucigalpa, said CIA officials rebuked him several times because his declarations contradicted what Congress and the U.S. public were being told.

A congressional source said a number of legislators became increasingly uneasy last year about the contrast between what CIA briefers told them and what the insurgents were doing and saying. But they proved reluctant to challenge the administration, he added.

Ironically, revelation that the CIA directly carried out mining of Nicaraguan harbors, more than unease with the overall policy, tipped congressional sentiment toward suspension of funds, he said. Chamorro said that a CIA deputy station chief in Tegucigalpa came to him late one evening in January with a prepared communique that he ordered Chamorro to have broadcast over the rebel radio.

The communique, which went on the air as scheduled, claimed the rebels had mined Corinto harbor. A similar procedure was carried out for the February rocketing of a Salvadoran rebel radio facility in western Nicaragua, Chamorro said. "Our participation was nil," he added.