TEGUCIGALPA (Reuters) - An agreement to end a four-month political crisis in Honduras collapsed on Friday after two rival leaders failed to form a unity cabinet to heal the damage from a June coup.

Ousted President Manuel Zelaya declared the pact dead just a week after it was signed and called on Hondurans to boycott presidential elections this month because, in a surprise move, de facto leader Roberto Micheletti said he would form a new government without him.

The failure of a U.S.-driven deal to end the crisis throws into question whether foreign governments will recognize the result of the November 29 presidential election and means any incoming government could inherit a chaotic political situation and be cut off from vital international aid.

The United States and the Organization of American States, or OAS, which had pushed the two sides into their agreement after months of delays, urged them to return to the table.

Zelaya and Micheletti had agreed to form a unity government by Thursday, but then they clashed over who would lead the cabinet until Congress decided whether to reinstate Zelaya.

"It is urgent that this government be created immediately," State Department spokesman Ian Kelly said in a statement, noting U.S. disappointment with recent developments.

OAS head Jose Miguel Insulza deplored the breakdown and said the democratically elected president should be restored "without further subterfuges."

Zelaya, who was toppled and sent into exile in a June 28 coup, said he would not go back to the negotiating table.

"It's impossible. The thing is completely worn out and it makes no sense to continue," he told a Chilean radio station from the Brazilian embassy in Tegucigalpa, where he has been holed up since sneaking back into Honduras in September.

Argentina and Brazil lined up against Micheletti. Brazil condemned "the delay tactics of the de facto government in Honduras" and said Zelaya was under no pressure to leave its embassy.

Outside the embassy, a heavy contingent of soldiers and military vehicles was deployed. Inside, Zelaya called for peaceful protests by his supporters around the country and told his long-faced supporters "only God knows what happens next."

AID SUSPENDED

The impoverished coffee and textile-exporting country has been isolated diplomatically and cut off from millions of dollars of international aid for social programs since the coup. The European Union said on Friday that it would not resume aid until the crisis was resolved.

Zelaya had declined to name any members to a unity government, saying it was offensive to form a cabinet when it had not been decided who would lead it, and Micheletti said he was going ahead without them.

"We've completed the process of forming a unity government ... It represents a wide spectrum despite the fact that Mr. Zelaya did not send a list of representatives," Micheletti said in a televised speech.

Ministers from the de facto cabinet resigned to make way for the new government, which Micheletti said will include names put forward by different political factions.

The Honduras crisis has brought back unwelcome memories of decades of military regimes, human rights abuses and political instability that plagued Latin America during the Cold War.

The United States and the OAS had celebrated last week's accord, but it turned out to be too vague and contradictory to be successful.

Zelaya insisted the November 29 election will not be legitimate unless he is first restored to power to finish the rest of his term to January. But the accord did not guarantee his return.

The agreement left it up to the Congress to rule on Zelaya's return to the presidency, but lawmakers were not given any deadline and dragged their feet on convening for a vote.

Once the accord was signed, Washington agreed to recognize the November election result even if Zelaya was not reinstated, giving up on earlier demands that he first return to power.

Latin American leaders are unlikely to recognize the election result under current circumstances, however.

Zelaya was forced into exile by the military after the Supreme Court ruled in secret that he had illegally launched a drive to hold a referendum to gauge public interest in changing the constitution. Critics said he wanted to extend term limits, which he denies.

Congress quickly installed Micheletti as interim leader, but his government has failed to win recognition abroad, and human rights groups have documented abuses including deaths and the suspension of civil liberties.

(Additional reporting by Gustavo Palencia, Sean Mattson and Mario Naranjo; Editing by Kieran Murray and Mohammad Zargham