Adolfo Calero, leader of the largest group of U.S.-backed Nicaraguan rebels, was quoted yesterday as saying he wants to increase his troops from the current total of 15,000 to about 25,000.

Calero told The Miami Herald that he would need $50 million in U.S. aid to accomplish the expansion of his Nicaraguan Democratic Force. According to a transcript of the interview with reporter Alfonso Chardy, Calero said the funding would "help us continue and grow up and upgrade . . . . I'd like to get $50 million; then we'd be in business."

The administration has proposed that the CIA be given $14 million to maintain the rebels this year at roughly their current strength. "That's peanuts, you know. That's certainly not enough" to expand or to deal with Nicaragua's new Soviet-supplied MI24 helicopters, Calero said.

But the $14 million request faces a stiff fight when it comes up next March in Congress, which last year cut off rebel aid completely.

Expansion along the lines Calero seeks would be a major escalation of U.S. involvement in military action against Nicaragua. State Department officials have repeatedly denied plans for any such escalation.

Calero also told The Herald that he wants the United States to sever diplomatic ties with the leftist Sandinista government of Nicaragua and to impose a trade embargo.