Military strongman Gen. Manuel Antonio Noriega is facing unprecedented political isolation in Panama after a stormy break this month with one of his oldest and closest advisers, according to Panamanian and American participants in the events.

The firing Thursday of the Panamanian consul general in New York, Jose I. Blandon, brought to light a three-month-old, behind-the-scenes effort by Blandon to negotiate a political settlement involving Noriega, the Panamanian opposition and the United States. In the process, Noriega, who controls the government as commander of the Panamanian Defense Forces, entertained the possibility of leaving power this year, possibly as early as April.

Noriega's feud with Blandon opened, for the first time, a public rift in the government party over the general's tenure. The government Democratic Revolutionary Party had been the only influential civilian group still supporting Noriega. Blandon is a longtime, and powerful, member of the party.

The dispute, according to the participants in the events, also sent shock waves through the Panamanian Defense Forces, where Blandon enjoys many close ties. However, no open dissension has surfaced among senior active-duty officers, whose continued loyalty to their commander has sustained Noriega through seven months of protests against him mounted by opposition groups.

Noriega blames Washington for fomenting the opposition to him in order to roll back the 1979 treaties that will give control of the Panama Canal to Panama in 2000. He has chilled Panamanian-U.S relations almost to the freezing point. In late December the Reagan administration dispatched Pentagon official Richard Armitage to Panama to tell Noriega that U.S. policy is to encourage him to step down.

But the story of the Blandon Plan, as the former consul's efforts are called, shows that Noriega has continued to try to parley with the Reagan administration about his future.

Many details of Blandon's strategy for guiding Panama out of the Noriega crisis are laid out in an Oct. 27, 1987, draft document and in photocopies of several memorandums that were passed back and forth between the consul and the general late last year. They were made available to The Washington Post by Panamanian opposition sources.

Blandon did not return numerous phone calls to his New York residence.

Earlier this month, Noriega publicly branded Blandon a traitor, and last week Blandon, fearing retaliation against his family, hastily arranged for his 21-year-old son to flee Panama.

Blandon's position is unusual because he insists that he has not defected to the opposition, but remains in the leadership of the government party, which is a front for the Panamanian Defense Forces. Last week, the progovernment newspapers in Panama, which are controlled by Noriega and the Democratic Revolutionary Party, dropped all rhetoric attacking Blandon, a sign of internal party debates over the former consul and his plan.

Despite his dismissal, "his plan is still very much alive and gathering momentum," said a Reagan administration official.

Opposition leaders and American officials and lawmakers said Blandon told them that Noriega asked him in mid-1987 to devise a contingency plan for a transition government that would allow Noriega to step down gracefully.

In his plan, Blandon outlined reforms that he felt were necessary to achieve a rapid transition to full civilian rule and forge a more professional, apolitical army. In practice, the current president, Eric Arturo Delvalle, is only a figurehead. Blandon insisted in the October document and in many conversations that the canal treaties could not be touched.

Noriega "must set the time of his own retirement," the October document said, but it would be no later than the first week of April.

Under the plan, Noriega would agree, before departing, to order into retirement all Panamanian Defense Forces officers who have completed 25 years of service. This would eliminate all but one or two senior officers who comprise Noriega's inner circle and for whom he has waived mandatory retirement rules.

In Blandon's scenario, Noriega would be succeeded by the next highest eligible officer in the heirarchy, Col. Elias Castillo. Delvalle would retain his position as president during a year-long interim leading to May 1989 elections organized by an independent electoral tribunal, to be chosen by agreement with the opposition.

In a telephone call from New York to a radio station in Panama that was broadcast live last week, Blandon explained, "I drew up a document which the Panamanian government has seen. It was not prepared by the United States. With it, I held a series of conversations, authorized by Panama's government, with American lawmakers and State Department officials to lay the groundwork for an understanding. . . . Is that treason?"

A U.S. official, commenting on the Reagan administration's response to Blandon, "We just said we were interested but we weren't getting involved. We said, like a broken record, that the Panamanians have to sort this one out themselves."

Blandon's sought to probe whether Noriega, if he sought exile outside of Panama, would still face prosecution from three investigations under way in Florida into drug and money-laundering allegations against him. But U.S. officials made no promises.

An administration official who met with Blandon said, "No one in the federal government gives assurances about what a grand jury or a district attorney will do. Probably Noriega's best bet is to strike some agreement to live out his retirement in Panama."

Last fall, Blandon also met in the United States with three opposition figures to discuss his plan. Two are key opposition exiles -- former ambassador to Washington Gabriel Lewis and Roberto Eisenmann, publisher of the closed opposition daily La Prensa. The third opposition leader, Roberto Arias Calderon, still lives in Panama.

Opposition sources said Arias traveled quietly to Miami for the meeting. Blandon said on the radio that Noriega personally authorized the contacts.

The Blandon Plan is "the only serious blueprint to emerge in the whole crisis. It's value was that it was developed by someone in the government," Lewis said.

But late last year, Noriega began to have second thoughts.

In mid-November, retired admiral Daniel Murphy, Vice President Bush's former chief of staff who has made speeches supporting Bush's presidential efforts, traveled to Panama with Tongsun Park, the South Korean businessman involved in a Washington bribery scandal 10 years ago.

Congressional staffers said Murphy told them after he returned that he held a one-on-one meeting with Noriega.

Efforts to reach Murphy for comment were unsuccessful.

The staffers said Murphy told them he was pursuing private business opportunities in Panama.

Noriega, however, chose to describe Murphy later to some of his close associates as a U.S. government envoy, one of them said. The general seemed heartened that he might be finding new support in Washington, this associate said.

On Dec. 7, Blandon cabled to Noriega the most recent draft of his plan. Two days later, Noriega wired a memo to New York praising Blandon and calling the plan "valuable." But he added that he did not want to be like "the Japanese empire in World War II, signing its capitulation on the decks of the Missouri."

Abruptly, on Dec. 21, Noriega telephoned Blandon in New York to tell him to halt his efforts. Blandon wired back a memo warning Noriega that if he sought only to protect his personal interests, "history will forget you."