MIAMI, FEB. 8 -- Nicaraguan rebel leaders, scrambling for a survival strategy in the wake of congressional refusal last week to appropriate new aid funds, pleaded today for independent financial contributions from U.S. supporters to two private foundations based in Washington.

The contra leaders said Republican presidential candidate Robert Dole recently contributed $500 to rebel coffers, and Sen. John McCain (R-Ariz.) donated $400. Adolfo Calero, one of four directors of the Nicaraguan Resistance who spoke at a press conference here, thanked the politicians.

The leaders also announced that they have postponed scheduled negotiations with the Nicaraguan government because the Roman Catholic cardinal who is the mediator is unavailable and because of the impact of the defeat of the aid package. The delay will be for only "a few days or a couple of weeks," according to another contra director, Alfredo Cesar.

Calero warned that the aid cutoff in the House of Representatives had removed pressure on the Sandinistas.

To partially replace the $36.2 million appropriation rejected last week, the directors said they have set up the Nicaraguan Resistance USA Office and the Nicaraguan Resistance Educational Foundation in Washington to take advantage of private donations.

Cesar refused to say how much money was needed or anticipated, but pledged that the funds raised would be handled in an "orderly, legal over-the-table fashion."

Calero emphasized, however, that "private funds can never match the U.S. government allotment for the resistance."

He said the foundations would reveal the names of donors who so agreed.

The money raised in the United States would be used only for non-lethal aid, the contra leaders said, adding they will seek aid for weapons elsewhere.

"We will go to third countries and people living outside the United States" for funds to buy weapons, said Calero, but added no other nations have yet been approached.

Another idea under consideration by the contras is floating bonds similar to the Israel Bonds sold in the United States to support that nation, Calero said.