Honduras has been suffering from a political crisis for four months
A deal to resolve the political crisis in Honduras is "dead", ousted President Manuel Zelaya has said.
He was speaking after interim leader Roberto Micheletti said he was forming a "unity government" without Mr Zelaya's representatives.
The US government has expressed its disappointment over the breakdown of the accord, which they helped broker.
Honduras has been shaken by a political crisis that began when Mr Zelaya was forced out of the country on 28 June.
Speaking to journalists on Friday, State Department spokesman Ian Kelly said it was urgent that a unity government be created "immediately" and called on both sides to return to the negotiating table.
He said the US government was "disappointed by the unilateral statements" made by Mr Zelaya's and Mr Micheletti's negotiating teams on Thursday.
Mr Micheletti acted as a deadline passed for putting a power-sharing agreement into effect.
The two rivals agreed to a power-sharing deal last week, with a deadline for it to be implemented by midnight on Thursday (0600 GMT Friday).
But Mr Zelaya had warned on Thursday that he would withdraw from the deal unless Congress held a vote on his restoration to power.
He has said elections planned for 29 November will not be valid unless he is restored to power first, though the agreement did not guarantee the ousted leader's restitution.
Interim authorities did not consider the Congressional vote demanded by Mr Zelaya to be an essential part of the agreement.
They said the agreement set a deadline for the formation of a government, but not for Congress to meet.
As the power-sharing deadline passed, Mr Micheletti said he had "finalised the process of confirming a unity government".
"Everybody, with the exception of Mr Zelaya, recommended Hondurans to lead the institutions of our country as part of the new government," he said.
Though Mr Zelaya had not submitted a list of names, Mr Micheletti said the government was "representative of a large ideological and political spectrum in our country and complies strictly with the agreement" signed last week.
Mr Zelaya, who has been sheltering in the Brazilian embassy since his return to Honduras in September, responded by pronouncing the accord "dead".
"It's absurd what they are doing, trying to mock all of us, the people who elected me and the international community that supports me," he said.
"We've decided not to continue this theatre with Mr Micheletti."
Mr Zelaya was ousted after planning to hold a non-binding public consultation to ask people whether they supported moves to change the constitution.
His critics said the move was unconstitutional and aimed to remove the current one-term limit on serving as president and pave the way for his possible re-election.