Nicaraguan rebel leader Eden Pastora said yesterday that he is trying to mount a political challenge to the Nicaraguan government, but he left open the possibility of reconciliation with the Sandinistas.

Pastora, who arrived here yesterday, ruled out joining forces with the U.S.-backed contras fighting the Nicaraguan government.

The contras, or counterrevolutionaries, "have no chance whatsoever of military or political victory," he said.

Pastora, who quit fighting the Sandinistas in May after refusing to join the contra umbrella group, United Nicaraguan Opposition (UNO), said his political efforts hinge on how much support he obtains from "our democratic friends in Latin America and Europe."

He is in Caracas to seek funds from Venezuelan allies and possibly to meet with a number of sympathetic world leaders visiting Venezuela this week on their way to the Socialist Internationalist Congress in Peru.

Among those scheduled to visit Venezuela are Israeli Prime Minister Shimon Peres, Italian Prime Minister Bettino Craxi, former West German chancellor Willy Brandt and Norwegian Prime Minister Grow Harlem Brudtland.

"I have ended an armed struggle, but a political battle is possible," he said.

He said he would restore ties with Nicaragua's government, with which he broke in 1981, if "the Sandinistas return to the original plan of the revolution, to be democratic, nationalistic and truly Sandinista."

Pastora, also known by his nom de guerre, Commander Zero, ruled out joining UNO to fight the Nicaraguan government. "Their military and political tactics are Somocista," he said, referring to followers of the late Anastasio Somoza, Nicaragua's dictator until the Sandinistas toppled him in 1979. "Their commanders are Somocistas, and as proof of their criminal strategies, during four years of guerrilla warfare, they haven't turned one prisoner over to the International Red Cross."

Pastora also blasted the Reagan administration, which supports UNO and criticized the rebel leader for refusing to join.