Secretary of State George P. Shultz refused yesterday to say whether the administration will ask other countries to provide aid to Nicaragua's contra rebels if Congress rejects President Reagan's request for $36.3 million to support them in their fight against the Marxist-led Sandinista government.

But Shultz left unclear whether the administration is considering such an option or whether he was merely reluctant to say anything implying that he expects this week's showdown vote on contra aid to go against Reagan.

In a television interview, Shultz evaded several attempts to get him to deny categorically that no thought is being given to asking other nations for contra aid. Instead, he parried the questions with assertions that he and Reagan will "never give up on peace with freedom in Central America," that he saw no reason to answer "iffy" questions and that to talk about possible fallback strategies would be an admission that the administration has lost the upcoming congressional battle.

The Miami Herald has quoted unidentified U.S. officials as saying that if the administration loses the House vote on contra aid Wednesday, it is weighing the possibility of soliciting other governments for funds and supplies to keep the contra movement alive.

That report rekindled memories of the Iran-contra affair. Investigations revealed last year that when Congress cut off aid to the contras on an earlier occasion, the administration went to other countries -- including Saudi Arabia, Israel and Brunei -- to fill the gap with secretly provided assistance.

Both Shultz and Reagan's national security adviser, Lt. Gen. Colin L. Powell, were asked about the Herald report during television appearances yesterday. Powell, speaking on NBC's "Meet the Press," replied: "I'm not aware of any such plan. We will abide by the will of the Congress."

But when the question was put to Shultz on ABC's "This Week With David Brinkley," he raised eyebrows among his questioners with his initial answer. He said:

"There isn't any basis for that statement. But there certainly is a basis for saying that as far as President Reagan is concerned, and as far as I'm concerned, I'm never never going to give up on peace with freedom in Central America. Those are important objectives for us, and we'll keep trying. And I don't even want to contemplate the kind of outcome that goes with pulling out the rug from a strategy that has produced where we are now."

When a reporter pressed him further about whether that meant he was not ruling out third-country aid, Shultz said, "Why should I answer an iffy question like that?"

However, following a commercial break, Shultz elaborated by adding:

"The reason that I didn't want to answer your question is that the minute you start talking about what you're going to do if you lose, you've lost. And I intend to win. And the president intends to win. That's our orientation."

While Shultz and Powell insisted that the vote is still undecided, House Majority Leader Thomas S. Foley (D-Wash.) said on "Meet the Press," "I'm very sure we're going to win . . . . I'm firmly convinced that the aid will be rejected."

Rep. Tony Coelho (D-Calif.), appearing on the Brinkley show, said that as of yesterday, the Democrats had the votes to beat the aid request, and he added that he believes that will be the case Wednesday.