SAN SALVADOR, AUG. 21 -- After a five-hour meeting today with Salvadoran President Jose Napoleon Duarte, Nicaraguan rebel leaders accepted a regional peace plan drafted by the five Central American presidents.

As soon as the meeting ended, however, Duarte and the leaders of the rebels, known as contras, gave differing interpretations of the contras' action.

In his first lengthy interview since the signing, Duarte tonight insisted that his appeal to the contras was "exactly the same" as his request to El Salvador's leftist guerrillas. "I'm saying the same thing to both, to accept the peace plan and join in the democratic process," Duarte said.

Under the plan, the rebels fighting Nicaragua's Marxist government would be required to accept an amnesty and forgo further U.S. aid. The contras emerged from today's meeting, however, saying there had been no talk of laying down their arms.

"At no time are we talking about laying down our arms," said contra leader Alfredo Cesar, adding that Nicaragua must first institute a series of democratic reforms called for by the peace plan.

The six leaders of the Nicaraguan Resistance, the main contra alliance, said in a statement, "We accept the historical challenge to fight for democracy in our country . . . . We accept the Central American presidents' peace plan."

But Adolfo Calero, the contras' civilian leader, said the Nicaraguan Resistance accepted the peace plan in part because they doubt the Sandinistas will comply with it. "I just don't think they will do it," Calero said.

The peace plan was signed Aug. 7 in Guatemala by the presidents of Guatemala, Nicaragua, El Salvador, Honduras and Costa Rica.

The contras proposed a meeting Sept. 15 in Managua with Sandinista government leaders to discuss a cease-fire that was mandated in the accord to begin on Nov. 7.

The contra leaders stressed that Nicaragua also must be made to comply with the Guatemala pact.

"We want peace but not at the expense of our freedom," they warned.

Today's meeting, the first public encounter between Duarte and the contra leaders, was prompted by a speech that Duarte made last week in which he called for simultaneous talks between the Nicaraguan government and the contras and between his government and the leftist Salvadoran guerrillas of the Farabundo Marti National Liberation Front.

He called on the two rebel groups to prepare to return to the political process of their countries and prepare to lay down their arms Nov. 7.

But in a news conference after today's meeting, contra leaders said they are not for the moment considering laying down their weapons or renouncing armed warfare as a means to power.

"The situation in El Salvador is totally different from Nicaragua, where there is a totalitarian government," contra leader Pedro Joaquin Chamorro said. "It isn't logical for us to lay down our arms until we see that democratic conditions have been restored to our country."

The Guatemala accord calls for an end to foreign aid for guerrilla groups in the region, a return to full democracy in each country, internal dialogues between the governments and their unarmed political opponents and a regional cease-fire.

Under the terms of the plan, Nicaraguan President Daniel Ortega is not required to talk with the contras. The Sandinista government has repeatedly refused to do so, saying the contras are a creation of the United States and that only Washington can seriously negotiate the end to fighting in Nicaragua. The Sandinistas opened a tentative dialogue with civilian opposition parties earlier this month.

Duarte's proposal for a peace dialogue between the Salvadoran government and the leftist guerrillas has been stalled because the Salvadoran rebels refused to accept the aspects of the peace plan that require them to accept a government amnesty and give up their fight.

The Salvadoran guerrillas have now become the only group in Central America to reject the Guatemala plan. But Duarte's willingness to accept more minimal support for the accords from the contras revived dwindling hopes for talks between the Salvadoran government and the guerrillas.

During much of the long meeting, Duarte and at least five of his top advisers reportedly lectured the contras about the meaning of the plan.

The president said he told the contras "absolutely firmly" that he would not allow Salvadoran soil to be used for activities in support of their forces.

The Ilopango military air base in El Salvador was the headquarters of a secret resupply operation for the contras last year that was revealed in the Iran-contra affair. In the interview, Duarte argued that he never agreed on any help to rebel groups, but that the commander of the Ilopango base, Gen. Juan Rafael Bustillo, had made his own decision to support the operation because Duarte had not issued a specific order against it.

"When the case came up, I issued a categorical order it shouldn't happen again," Duarte said.

Duarte, a close ally of the Reagan administration, declined to comment on whether Washington should give any more aid to the contras.

"I'm never going to say anything for or against the contras," he said. "That's an American headache, not mine. What I am saying very clearly is that I completely support the document I signed. And I demand that Nicaragua comply with it, too."

Duarte said Nicaragua has 10,000 political prisoners and El Salvador about 730, and that all of them have to be freed to comply with the pact.