WASHINGTON (Reuters) - Ousted Honduran President Manuel Zelaya on Tuesday accepted a U.S.-backed effort by Costa Rican President Oscar Arias to mediate an end to the political crisis in Honduras and said talks with his rivals would begin on Thursday.

“Our first meeting is set for Thursday, in Costa Rica,” Zelaya, told Honduran radio from Washington.

In Honduras, Roberto Micheletti, who was appointed president by Honduran lawmakers after the June 28 coup, also said he would attend Thursday’s talks under Arias’ mediation.

Arias, a Nobel Peace Prize winner with experience in solving Central American conflicts, faces mediating between sharply opposed positions.

Zelaya said his reinstatement as president was nonnegotiable.

“What this is is not a negotiation, this is the planning of the exit of the coup leaders,” he said.

But Micheletti maintained his position that Zelaya could not return as president. “We’re not going to negotiate, we’re going to talk,” he said. “We’re going into these talks because we’re interested in having peace and tranquility in Honduras.”

Zelaya, whose ouster was sparked by his efforts to change presidential term limits and by his political shift to the left, spoke after meeting U.S. Secretary of State Hillary Clinton.

She urged him to negotiate rather than try to force his way back into the country.

Zelaya had tried to fly home on Sunday, but the interim government stopped his plane from landing. At least one person was killed when troops clashed with pro-Zelaya protesters who went to the airport in the capital, Tegucigalpa, to meet him.

The coup in the impoverished Central American coffee and textile exporter has been widely condemned abroad, and posed a diplomatic challenge for U.S. President Barack Obama.

The Organization of American States took the rare step to suspend Honduras on Saturday after Honduras’ interim authorities defied its ultimatum to reinstate Zelaya. But the group has failed to find a solution to the crisis.

ARIAS ROLE

Arias declined to speculate about the prospects of success in the mediation.

“What I would like is not to let them leave until there is an agreement,” he said in the Costa Rican capital, San Jose.

Clinton said all issues should now be settled in talks with Arias, who won the Nobel Peace Prize in 1987 for helping to end political violence in Central America.

“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,” Clinton said of Zelaya.

Slideshow ( 28 images )

“So, instead of another confrontation that might result in a loss of life, let’s try the dialogue process and see where that leads,” she added.

While backing a restoration of “the democratic, constitutional order” in Honduras, Clinton did not explicitly call for Zelaya to return to power, saying this should be negotiated by the parties themselves.

Some analysts wondered whether the United States may be tempering its support for Zelaya, although Obama said he said he should return to power.

“America supports now the restoration of the democratically elected president of Honduras, even though he has strongly opposed American policies,” Obama said in a speech in Russia.

Slideshow ( 28 images )

“We do so not because we agree with him. We do so because we respect the universal principle that people should choose their own leaders, whether they are leaders we agree with or not,” he added.

The United States has repeatedly condemned the coup in Honduras, which has a population of 7 million and is the third poorest country in the Americas after Haiti and Nicaragua.

ARGUMENTS FOR OUSTER

Defying the international pressure, Micheletti has insisted Zelaya was legally removed.

Micheletti said in Tegucigalpa that if Zelaya returned to Honduras, it should not be as president but to face charges in the courts. “He committed crimes and he must pay for them,” he said.

Micheletti’s interim government says the ouster was a constitutional transition carried out by the army and supported by the Supreme Court because Zelaya had illegally tried to organize a vote on changing presidential term limits.

Zelaya took office in 2006 and had been due to leave in 2010. He had riled the country’s traditional ruling elite with his leftward shift and growing alliance with Venezuela’s socialist president, Hugo Chavez.

In the Honduran capital, several thousand anti-Zelaya demonstrators packed into a main plaza, waving blue and white national flags and posters ridiculing Chavez, who many accused of meddling for backing Zelaya -- nicknamed “Mel”.

“We don’t want Mel back. Those people were going to take us to socialism,” said Carlos Ramos, a teacher and retired air force officer who was taking part in the protest.

Several thousand supporters of Zelaya led by his wife, Xiomara, staged their own rally.

“They say there is peace in the country, but how can there be peace if people cannot leave their neighborhoods ... if there is a curfew, if they are suspending people’s rights and the army is out repressing the people,” Xiomara Zelaya said.