MEXICO CITY — A week after an accord mediated by the United States seemed to have unblocked the political standoff that had paralyzed Honduras since President Manuel Zelaya was deposed in a June coup, the agreement appeared to have collapsed early Friday, news reports said.

Mr. Zelaya, whose possible return to power was at the heart of the accord, is still a virtual prisoner in the Brazilian Embassy, where he took refuge six weeks ago after he secretly slipped back into Honduras. He is no closer to resuming his presidency, while the de facto president, Roberto Micheletti, and the people around him are still running the country.

The accord also set Thursday as a deadline to name a unity government that would oversee preparations for a presidential election scheduled for later this month.

But none of this has happened. Critics said the accord was difficult to enforce since its only source of pressure was an American threat not to recognize the planned election.

Mr. Zelaya said early on Friday that the accord failed after Mr. Micheletti, the de factor (sic) president, moved to form a new government without him, Reuters reported. Mr. Zelaya declined to name any members to the cabinet and Mr. Micheletti said he was going ahead without them. “We’ve completed the process of forming a unity government,” Mr. Micheletti said in a televised speech quoted by Reuters. “It represents a wide spectrum despite the fact that Mr. Zelaya did not send a list of representatives.”

Mr. Zelaya said through a spokesman that the pact was dead and blamed the de facto government for its failure, Reuters said. Mr. Zelaya seemed unlikely to be returned to office.

As part of the deal, both Mr. Zelaya and Mr. Micheletti had agreed to put the question of Mr. Zelaya’s return to a vote in the Honduran Congress. But the accord set no deadline, and congressional leaders have yet to decide on a date for a vote.

After threatening that it would not recognize the presidential election scheduled for Nov. 29 unless Mr. Micheletti signed on to the deal, the Obama administration hinted that it would accept the results even if the accord’s terms are not fully met.

“The bottom line is there will be no reversal of the coup d’état,” said Kevin Casas-Zamora, a former vice president of Costa Rica and an analyst at the Brookings Institution. “That cannot count as a diplomatic success.”

American officials dismiss that conclusion, arguing that both sides have agreed to abide by Congress’s decision and that an election will resolve the crisis.

The divisions in Honduras were on display on Thursday in Tegucigalpa, the capital, where Mr. Zelaya’s supporters were camped outside Congress to try to force a vote on his return.

Regional splits are also appearing over how long the Honduran Congress can delay the vote and what the legislators’ eventual decision should be.

Ricardo Lagos, a former Chilean president who is on the verification commission set up to monitor the accord, said Thursday that Mr. Zelaya should be returned before the election.

Critics say the de facto government appears to be stalling, expecting that once the elections go ahead, the international community will recognize them.

What is more, they say, Mr. Shannon’s remarks on recognizing the elections leave the Obama administration with little leverage to enforce the accord. Christopher Sabatini, senior director for policy at the Council of the Americas, in New York, said that the Obama administration appeared willing to accept the elections’ outcome rather than admit that there was no guarantee when and how Honduran legislators would vote.

Richard Berry contributed from Paris.

New York Times