Rafael Pineda, who as minister of the presidency is No. 2 in the interim government headed by Roberto Micheletti, told Reuters the administration was "firm, unchangeable" against Zelaya's return to power.
In neighboring Nicaragua, the exiled Zelaya said he asked a U.S. delegation to step up measures against the leaders of the June 28 coup that ousted him and that he planned to take his case to the International Criminal Court.
With mediator Costa Rica's attempts to resolve the crisis making little progress, Micheletti, who has been named interim president by Congress, has asked for a special envoy to come to Honduras "to cooperate in the start of dialogue in our country."
The coup leaders are under pressure from Washington to reinstate Zelaya and a source close to the de facto government said Micheletti might consider letting Zelaya come back if there were assurances he would not try to derail democracy.
But Pineda rejected a return to office for Zelaya, who upset conservative critics in recent months by allying with socialist Venezuelan President Hugo Chavez.
"The position of the government in this issue is firm, unchangeable," Pineda told Reuters. "The agreement, if there has to be one, can only happen if President Zelaya is not reinstated in the presidency of the Republic."
Central America's most serious political crisis in nearly two decades has created a test for U.S. President Barack Obama as he tries to define his relationship with the region.
Obama has been pressured by Republican senators who want him to clarify his policy toward Honduras. Republican Senator Jim DeMint has threatened to delay a Senate vote on a nomination for a key State Department post for Latin America because of U.S. support for leftist Zelaya.
Washington has revoked diplomatic visas for four members of Micheletti's administration to pressure it to reverse the coup, which has been condemned by Latin American governments and the U.N. General Assembly. International loans and U.S. military aid have also been frozen.
Pineda said the de facto government was committed to dialogue but also ready to hold out until a November presidential election if talks do not produce a deal.
He said Micheletti could quit as part of an accord Costa Rican President Oscar Arias is trying to broker, but only on the condition that Zelaya resign as well.
High-profile Envoy
The interim government's foreign minister Carlos Lopez echoed Pineda's stance against Zelaya's return to power, saying the government was willing to endure tougher sanctions and hold out until elections scheduled for November.
"This country can survive in the most dramatic scenarios," he told Reuters. "The people might eat less but fasting in all religions is good for the body and the spirit."
Micheletti has asked Arias to send a high-profile envoy, possibly former Inter-American Development Bank head Enrique Iglesias, to Honduras to breathe life into the talks.
Honduran political analyst Juan Ramon Martinez said Micheletti might be trying to float a more flexible image to the outside world while entrenching his position at home.
"I think what they are doing is ensuring that the dialogue drags on so the negotiation won't die but it won't move forward either," said Martinez, a former presidential candidate with close connections to the Micheletti government.
The interim government has said it will abide by the decision of the Supreme Court, which is due to rule in the coming days on Arias' proposal that Zelaya be allowed back to serve out the rest of his term, which ends early next year.
"If he comes back it will be more of a symbolic return in order to get international aid flowing again ... Perhaps we are now seeing the light at the end of the tunnel but it's a long tunnel," said Eurasia Group analyst Heather Berkman.
Zelaya upset the Supreme Court and many in Congress by trying to hold a referendum to change the constitution. Critics say he was trying to extend his mandate but he denies that.
He has left Nicaragua's border area with Honduras where he had tried to stage protests against the coup. He returned to Nicaragua's capital, Managua, and met on Thursday with officials at the U.S. Embassy.
His supporters have sporadically blockaded highways in Honduras, an exporter of coffee and textiles, in mostly calm protests as the police have kept their distance.
But on Thursday, soldiers and police in riot gear dispersed protesters in the capital with tear gas and shots, injuring several people. At least one had a serious bullet wound, a doctor at the capital's main hospital said.
Police said dozens were detained. A protest leader said among those being held by police was a leftist candidate for November's election.
