The top anti-Sandinista leader urged the Reagan administration today to aid his insurgency by walking out of talks on accommodation with Nicaragua and cutting off trade and diplomatic relations with its Sandinista government.

Adolfo Calero, head of the Nicaraguan Democratic Force, said the administration could take these steps even if Congress refuses to renew U.S. financial backing for the rebel movement, halted last spring after expenditure of approximately $80 million by the CIA since 1981.

Reluctance in Congress to approve more CIA aid for the rebels has raised questions whether the insurgency can endure and, if not, where this leaves the administration's policy toward Nicaragua. U.S. backing for the rebels has been a major feature of efforts to force the Sandinistas to halt support for rebel movements in neighboring countries such as El Salvador.

Calero, in a news conference here, said the rebel movement needs renewed U.S. aid to further its goal of overthrowing the Sandinista government. But he asserted that the insurgency will continue even if the aid is refused, expanding the financial support from private and foreign sources that it has received since last summer.

"We have been doing it for close to seven months already," he said. "As U.S. government support dwindled, other kinds of support increased."

As an example, Calero said he received a telephone call 10 days ago from a man speaking Spanish with an accent who described himself as an intermediary for a wealthy individual who wants to give money to the rebels. After a meeting, Calero added, the intermediary agreed to deposit money on behalf of his principal in an "offshore" bank account. The money will be spent on antiaircraft missiles, such as SA7s or Redeyes, to counter Nicaragua's recently delivered Mi24 Hind helicoper gunships, he said.

Calero has said previously that his Nicaraguan Democratic Force, the paramount rebel group, has raised slightly more than $3 million and obtained $900,000 worth of equipment since CIA funding dried up last summer. He has refused to detail the new aid sources, except to describe them as private individuals in the United States and "political sectors" abroad.

Congress agreed to a compromise last October in which it approved another $14 million for CIA aid to the rebels in the 1985 fiscal year only on the condition that none of the money could be spent unless approval is renewed in March. Judging by statements from key congressional leaders, that approval has become highly doubtful in the House of Representatives.

Against this background, Calero said the Reagan administration can do several things without depending on congressional purse strings.

First, he said, the United States should pull out of the periodic talks with Nicaraguan representatives in the Mexican resort of Manzanillo.

In addition, Calero said the administration should halt trade with Nicaragua to further weaken its economy. Despite the "secret war," U.S.-Nicaraguan trade in such items as bananas, coffee and shellfish has continued, reaching $325 million last year.