Three Paris lawyers with longstanding connections to Iranian revolutionaries have moved to the center of the intricate international negotiations under way in an effort to win the freedom of Americans held hostage in Tehran.

Much of their movements and discussions during the 101 days that an estimated 50 Americans have been held captive in the U.S. Embassy in Tehran remain shrouded in secrecy.

It has become clear in recent days, however, that the legel help they once offered Iranian revolutionary leader Ayatollah Ruhollah Khomeini and his followers in exile could become the key to finding a formula to resolve the crisis.

By chance, one of the Paris lawyers is also the European counsel for Panama, the nation that deposed shah Mohammad Reza Pahlavi has chosen for his own exile. The lawyer, Christian Bourguet, may be well positioned if a deal is to be worked out involving an extradition hearing for the shah and a release of the Americans.

[Diplomatic sources at the United Nations told The Washington Post yesterday that efforts to reach a solution to the crisis are now "in the decisive week, not necessarily for the release of the hostages but in the sense of finalizing a solution," American sources echoed this view, saying that a plan offered this week by Iranian President Ahol Hassan Bani-Sadr appeared to open the way for a compromise.]

In telephone conversations, none of the partners would comment in detail on the efforts under way to resolve the Iranian-American, crisis for fear of compromising them.

Although Khomeini thus far has rejected any mediation, a high-level, at times overlapping exchanges are known to involve Iran, Panama, the United States and U.N. Secretary General Kurt Waldheim.

Complicating the efforts involving the Panamanian extradition procedure and a U.N. fact-finding commission is a rival plan that Bani-Sadr appeared to favor in an interview with the French newspaper Le Monde yesterday.

That plan apparently basically seeks to establish American responsibility -- indeed guilt -- for everything that went wrong during the shah's long rule in Iran.

The plan's leading foreign proponent is another French lawyer, Nuri Albala, a communist who describes it as a "Third World Nuremberg in an illusion to the Allied war crimes trial of leading Nazis after World War II.

Critics claim this approach would involve a drawn-out procedure damaging to the U.S. government and excellent propaganda for the Kremlin.

The Panamanian-U.N. option backed by the three French lawyers would limit itself to a relatively rapid grand jury-style investigation of the shah's alleged misdeeds.

Sources involved in some of the contacts were at a loss to explain Bani-Sadr's preference for the Albala option since the Iranian president long has been on record as favoring a rapid solution to the Iranian-American crisis to allow Iran's revolution to move ahead.

However, some observers suggested Bani-Sadr's remarks in Le Monde may have been dictated by a desire to protect himself from critics within the Revolutionary Council he heads and from the radical fundamentalist students holding the American hostages.

Since the shah's arrival in the Panama, Iran's extradition demand has under-gone a major change of emphasis.

Originally, it was seen as a way to air Iran's jeeply felt grievances against the shah and the United States. But early in January, Waldheim and pointed toward a fact-finding commission that would likely attract world attention.

The Panama connection remains important, however. The extradition request is the first time revolutionary Iran has agreed to follow international legal norms in the matter -- rather than threatening to send squads abroad to kill the shah if he were not returned.

Iran formally asked for the shah's detention pending presentation of the formal extradition request, which must be received within 60 days, according to Panamanian law.

So far Iran has yet to produce its formal request, apparently because of difficulties in compiling it.

Technically, the shah will become a free man if Tehran fails to produce the brief within the prescribed time period.

No extradition treaty exists between Panama and Iran, according to Panamanian law, any extradition decisions are the preorogative of the executive branch.

Traditionally, however, panamanian presidents have asked -- and followed -- nonbinding advice from the Supreme Court in such cases.

The final outcome is not in much doubt, because Panamanian law forbids extradition on political grounds or if the person involved risks the death penalty in his home country.

Observers noted that in his Le Monde interview Bani-Sadr made no mention of the shah's physical return to Iran.

Nevertheless, the extradition procedure is deemed important to back up Iran's formal demand that the shah be returned in exchange for freeing the hostages.

"It's a must for the Iranians to carry through with the extradition procedure on pain of making a spectacle of themselves," a lawyer said.

Left unsaid was the face-saving knowledge that any Iranian government could use the Panamanian government's decision as proof of its serious efforts to obtain the shah's extradition.

Panama, oddly enough, seems predestined to play such a key role in the American-Iranian crisis. Close to the United States after the Carter administration's success in returning the Panama Canal, Panama is also considered a nonaligned nation in good standing.

As soon as the shah arrived in Panama, Iranian Foreign Minister Sadegh Ghotbzadeh, an old client of the Paris firm since the days the partners helped prevent his deportation from France, telephoned Bourguet, remembering his ties with Panama.

"I went to Tehran for instructions, then to Panama," Bourguet said.

Cheron has represented Iran's central bank in efforts to persuade French courts to free assets in French branches of American banks. Those assets were frozen at Washington's behest following the seizure of the hostages in November.

Vallette and Bourguet made two visits to Iran during the shah's reign as part of Western legal efforts to improve the lot of political prisoners and stop torture.