Ousted Honduran President Manuel Zelaya, clearly frustrated with stalled negotiations aimed at resolving the country's political crisis, issued an ultimatum Monday to the interim government to reinstate him or face unspecified "other measures."

Zelaya delivered his message at a news conference in Nicaragua, where he arrived Sunday night following a brief trip to Washington.

At the same time, the interim government installed by leaders of the coup that forcibly exiled Zelaya on June 28 tried to return life to normal, successfully urging tens of thousands of Honduran teachers and students to return to class Monday.

Interim President Roberto Micheletti said a Honduran negotiating team could return to the bargaining table as early as this weekend to try to end the stalemate caused by the coup. Two previous rounds of talks mediated by Costa Rican President Oscar Arias failed to produce a deal.

At the swearing-in ceremony of a new foreign minister Monday, Micheletti said his team of delegates was "ready for another meeting."

But Zelaya said that he was "giving the coup an ultimatum."

If the interim government does not agree to reinstate him at the next round of negotiations, he said, "the mediation effort will be considered failed and other measures will be taken." He did not specify what actions he might take.

Zelaya accused the Micheletti government of using the talks "as a means to distract attention," and said the interim regime had "systematically increased repression" against demonstrators, journalists and others.

Members of Micheletti's administration did not immediately respond to Zelaya's comments.

Arias set to announce new talks

A Costa Rican government official said Arias, the 1987 Nobel Peace Prize winner for his role in helping end Central America's civil wars, was preparing to announce the date for new talks.

The coup has drawn international condemnation and nations have urged that Zelaya be restored to his post as the democratically elected president.

Honduras' Supreme Court, Congress and military say they legally removed Zelaya for violating the constitution. They accuse him of trying to extend his time in office, which Zelaya denies.

About 38,000 teachers heeded a request to return to class Monday, but more than 20,000 remained on strike to protest the coup.

Daily demonstrations for and against Zelaya continue in the country, but turnout has fallen from several thousand to only a few hundred this week.

On Sunday, Micheletti's administration said it was lifting an 11 p.m. to 4:30 a.m. curfew that had been in effect for two weeks because it was no longer needed and had met its goal of restoring calm and curbing crime.