Mr Zelaya has three months of his term remaining
The interim leader of Honduras, Roberto Micheletti, has resisted calls by regional ministers and diplomats to restore ousted president Manuel Zelaya.
Delegations from a dozen countries across the Americas made the demand after arriving in Honduras to try to mediate between the two sides.
But in a meeting shown on Honduran television, Mr Micheletti said Mr Zelaya's removal from power was lawful.
Mr Zelaya is insisting he be restored to the presidency by 15 October.
The meeting, which came after initial talks with representatives of both sides behind closed doors, was broadcast live.
Diplomats were seen trying to persuade Mr Micheletti that the only way out was for him to give up the presidential chair and let his predecessor return.
Mr Micheletti was unconvinced, to the detectable exasperation of his guests, BBC Central America correspondent Stephen Gibbs says.
"You don't know the truth or don't want to know it," Mr Micheletti told the visitors.
"You don't want to know what happened before 28 June," he said, referring to the date of Mr Zelaya's removal from power and ejection from the country.
The interim president's position is that President Zelaya - who is currently holed up in the Brazilian embassy - was removed legally according to the Honduran constitution, and that to reverse that decision by decree would be illegal.
Mr Micheletti did say he would be happy to step down - but only if Mr Zelaya also renounced his claim to be president.
"If I am an obstacle, I will step aside, but I also demand that this gentleman (Zelaya) who has caused such damage to the nation also goes," he said.
Mr Zelaya's opponents accuse him of illegally trying to extend his rule, an accusation he denies.
Mr Micheletti also said that the presidential election on 29 November would go ahead, unless "we are attacked or invaded".
For his part, Mr Zelaya insisted that he should be restored to the presidency by 15 October, or the election should be postponed.
"If the president is not reinstated by 15 October, the electoral calendar should proceed according to the law, allowing three months of campaigning to allow equal competition and people's participation," a statement from Mr Zelaya said.
The foreign ministers and ambassadors are attempting to use the deadline of November's forthcoming elections to make the interim government change its mind.
If those elections are held without Mr Zelaya in power, they say, then Honduras will probably find itself with another government which is shunned by the outside world.
Out of time
The high-powered diplomatic team includes foreign ministers and deputy foreign ministers from about a dozen countries in the region, as well as Jose Insulza, chief of the Organisation of American States (OAS).
"Those who thought it was possible to depose a president and normalise life in the country before starting an election campaign should realise that this has not been possible," Mr Insulza said as talks began.
Canada's minister for the Americas, Peter Kent, said: "I sense that everyone involved understands that we are nearly out of time and that this crisis has to be resolved now."
Our correspondent says that finding a solution where both sides can claim to have won is perhaps the only way to end this crisis.
Mr Zelaya was sent into exile after trying to hold a vote on whether a constitutional assembly should be set up to look at rewriting the constitution.
His opponents said his actions were in violation of the constitution and aimed at removing the current one-term limit on presidents - a charge Mr Zelaya has denied.
He returned covertly to Honduras on 21 September and took refuge in the Brazilian embassy.