Costa Rican President Oscar Arias is to lead mediation to try to resolve the political crisis in Honduras.
US Secretary of State Hillary Clinton made the announcement in Washington after meeting ousted Honduran President Manuel Zelaya.
She said both Mr Zelaya and the interim Honduran leader, Roberto Micheletti, had agreed on the appointment. Mr Arias said talks would begin on Thursday.
Mr Arias won a Nobel prize in 1987 for helping end the region's civil wars.
"He is the natural person to assume this role," Mrs Clinton said.
Mr Arias told the BBC his aim would be to start a dialogue between the two men, who are due to meet in Costa Rica.
Hillary Clinton: "Let's try the dialogue process"
"You can call it a negotiation or simply a talk, a conversation, a dialogue but I want the two parties to sit around a table and discuss the issues," he said.
Mr Zelaya was ousted and forced out of Honduras at gunpoint on 28 June. An attempt to fly back to Honduras failed at the weekend when the authorities there blocked the runway at Tegucigalpa airport.
Washington has sharply criticised the use of violence by troops loyal to the interim authorities, which saw at least one Zelaya supporter killed on Sunday.
'Open to dialogue'
On Tuesday, Mrs Clinton said her meeting with Mr Zelaya had been productive.
"I reiterated to him that the United States supports the restoration of the democratic, constitutional order in Honduras," she said.
This is is not a negotiation, this is the planning of the exit of the coup leaders
But she stopped short of explicitly calling for Mr Zelaya to return to power, saying he should try to settle issues in talks.
"I believe it is a better route for him to follow at this time than to attempt to return in the face of the implacable opposition of the de facto regime," she said.
"So, instead of another confrontation that might result in a loss of life, let's try the dialogue process and see where that leads, and let the parties determine all the various issues as they should."
Mr Zelaya told Honduran radio that his reinstatement as president was "non-negotiable".
"What this is is not a negotiation, this is the planning of the exit of the coup leaders," he said of the talks.
In Honduras itself, Roberto Micheletti said: "We are open to dialogue. We want to be heard."
But the interim government insists that the return of Mr Zelaya to power is an impossibility.
At the moment it seems unlikely that any common ground on the key issue will be found, the BBC's Stephen Gibbs in Tegucigalpa says, although the pressure is on the interim government.
Our correspondent says that surviving in near total diplomatic isolation, with the consequent restrictions on credit, will make the interim government's ability to function difficult.
It is expected to be urged to accept Mr Zelaya's return to the presidency, with a commitment that he will not attempt to tamper with the country's constitution.
President Zelaya planned non-binding public consultation on constitutional change
29 June: US President Obama condemns the overthrow as illegal
4 July: Organization of American States suspends Honduras in protest at overthrow
5 July: Mr Zelaya's jet is turned back from Honduras and clashes with troops leave at least one person dead
7 July: Both sides agree to attend talks starting Thursday mediated by Costa Rican President Oscar Arias
Another option might be some form of national unity government, also with Mr Zelaya as president, our correspondent says.
Mr Micheletti's interim government was named by the Honduran Congress to replace Mr Zelaya's administration.
It followed Mr Zelaya's attempts to hold a non-binding public consultation on 28 June to ask people whether they supported moves to change the constitution.
Opponents said that could have led to the removal of the current one-term limit on serving as president and so pave the way for his possible re-election.
Mr Zelaya is an ally of the leftist Venezuelan leader, Hugo Chavez, and correspondents say any US support is aimed more at boosting his legal status as the elected president of Honduras than at backing him personally.
Regional body the Organization of American States (OAS) has already condemned the ousting of Mr Zelaya as a military coup, and suspended Honduras's membership.
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