The political leadership of the leftist guerrillas trying to overthrow the Salvadoran government will hold talks with President Reagan's special envoy Richard B. Stone "in the next few days, with an open agenda," and will meet with the Salvadoran government's National Peace Commission, the guerrillas' U.S. spokesman announced yesterday.

Alberto Arene, U.S. representative for the Revolutionary Democratic Front/Farabundo Marti National Liberation Front (FDR/FMLN) joint command, said "a representation" from the front would meet with Stone "in a Latin American country." Arrangements were made with the help of Costa Rican President Luis Alberto Monge and Colombian President Belisario Betancur, he aid.

In addition, Arene said, a secret "preliminary agreement" has been signed with a representative of themission to meet to discuss the date, location and agenda of formal talks. He declined to provide further detait officials said there is "no official word of any kind," but did not deny that talks would take place. "We stity is the best way to treat this whole issue and we will not be discussing Ambassador Stone's plans in advanc coalition of five leftist guerrilla groups has been trying to overthrow the U.S.-backed government of El Salvvernment set up the peace commission earlier this year and authorized it to try to bring the left into the political process and the elections that are tentatively scheduled for early next year.

Reagan appointed Stone in June to help bring the guerrillas and the Salvadoran govnt together to try to negotiate a solution to the civil war.

After Stone's initial effort to meet with the hip fell through in early July, he met July 31 with FDR chief Reuben Zamora in Colombia, with U.S. Ambassador to Colombia Lewis Arthur Tambs present. Arene said yesterday that that meeting had been "preliminary. This one will be the first of an actual dialogue."

The Reagan administration has maintained that it would not engage in direct talks with the leftist guerrillas but would only facilitate their conversations with the Salvadoran government. However, both Arene and Francisco Quinones, president of the three-member Salvadoran peace commission, said their talks were arranged without Stone's involvement.

Asked why the guerrillas still plan to meet with Stone, Arene said, "We have said we do not consider Stone an intermediary but a representative of one of the parties to the conflict."

Asked if Stone and the Reagan administration had agreed to talks under those conditions, he said, "Well, I suppose that they know very well they are part of the conflict and not intermediaries."

Quinones said in an Aug. 11 interview with the Los Angeles Times that he had exchanged two sets of letters with the guerrillas since May. "Stone's mission is parallel or complementary to our own efforts but not a substitute for them," he said.

Arene also read a formal communique from the joint guerrilla leadership denouncing U.S. military maneuvers in Central America as "an obstacle to a political solution" and "a further step in the unjustified U.S. intervention in the area." The communique demanded the suspension of the maneuvers and withdrawal of U.S. Navy ships from Central American coastal waters, but did not make contiks contingent on any such action.

"The FDR/FMLN reiterates its disposition to work for a negotiated politiclogue without preconditions, expecting from the U.S. government and the Salvadoran government signs that show egotiate," the communique said.