Zelaya and the caretaker president in the Honduran capital, Roberto Micheletti, have agreed to travel to Costa Rica and meet with Arias tomorrow, Arias said in a news conference in the Costa Rican capital, San Jose. "What is important is there is a willingness by both sides to sit down and negotiate," he said.

• The anger and polarization in Honduras, though, foreshadow difficult talks between the two men, who have both vowed to stand firm.

Speaking on Honduran radio from Washington, Zelaya said that his reinstatement as president was "nonnegotiable." "What this is is not a negotiation," he said. "This is the planning of the exit of the coup leaders."

The Obama administration's efforts to find a diplomatic solution to the crisis came two days after Zelaya attempted to reclaim his presidency by flying to the country's main airport. Troops kept his small jet from landing, and soldiers fired on demonstrators, killing two men and fueling the pressure for a negotiated solution. "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. "So, instead of another confrontation that might result in a loss of life, let's try the dialogue process and see where that leads."

The new route to defusing the crisis contrasts with the tough line proposed by Zelaya's close ally, President Hugo Chavez of Venezuela. After the June 28 coup, in which soldiers roused Zelaya from bed and put him on a plane out of the country, Chavez said he would "overthrow" the de facto government.

So far, US officials have taken a nuanced approach to restoring Zelaya, consulting with allies in Latin America and voicing support for the Organization of American States, which had unanimously voted to demand Zelaya's reinstatement. But Micheletti did not budge, even after the Washington-based organization suspended Honduras.

A senior administration official said that discussion then turned to finding a respected interlocutor. Arias' name came up, and yesterday morning, Clinton called the Costa Rican president and spoke to him about mediating. She then put the idea to Zelaya, who agreed. In Honduras, Micheletti had already asked Arias on Monday to consider playing a role, the administration official said.