OSLO, DEC. 9 -- Costa Rican President Oscar Arias called on the Reagan administration today to stop all aid to the Nicaraguan rebels, including humanitarian and other so-called "nonlethal" funding that it is expected to propose in the next week, and suggested that Congress should refuse to approve such a request.

Arias' appeal, made here on the eve of his receipt of the Nobel Peace Prize for his Central American peace initiative, was a change from his previous position on nonmilitary aid, which he had said did not violate "the spirit or letter" of the peace agreement signed by the five Central American presidents last August.

In a news conference, Arias said he would accept the prize on behalf of his small and faraway Central American nation. Because of the prize, he joked, "most of you will know a little more about my country. . . . I don't think you'll be able to confuse Costa Rica and Puerto Rico."

The peace prize, Arias said, was "also a tribute to the five Central American presidents," who were "able to show the world that rationality prevails over madness." It was, he said, "an encouragement for us that we are doing things right."

Arias said he remained optimistic that the plan, which has been implemented in stages since Nov. 7, would succeed. "I think the ball is still rolling," he said. "I am only complaining that it is perhaps not rolling fast enough."

He indicated that he expected more progress at the next meeting of the five Central American leaders, in San Jose on Jan. 16. Despite difficulties, he said, "everything has changed in Central America" since the accord was signed. "There is a new attitude, new behavior, a new environment."

But, Arias added, "even though it has advanced quite a bit, I am still not entirely satisfied. . . . Sometimes I feel somewhat impatient."

Arias appeared frustrated with the Reagan administration and with what he described as the "intransigence, inflexibility and intolerance" of the U.S.-backed Nicaraguan rebels, also known as contras, in negotiations with the Sandinista government.

Similar intransigence, Arias said, had been shown by leftist guerrillas in El Salvador in the face of negotiating overtures by Salvadoran President Jose Napoleon Duarte. But Arias was particularly critical of the attitude of the contras in last week's indirect talks with the Sandinistas.

In those talks, in the Dominican Republic, the contras rejected a Sandinista proposal for a cease-fire in which the rebels would gather in three specified zones within the country and hand in their weapons. Instead, they demanded armed control over almost half of all Nicaraguan territory.

"When you look at the list of conditions and prerequisites. . . you become very pessimistic," Arias said of the contras. "To start to dialogue or talk, they ask for too much, in order to give concessions later on. I don't think that is the best way to negotiate. . . . It was impossible for the Sandinistas to agree," he said.

Arias was also indirectly critical of the intermediary for the talks, Nicaraguan Cardinal Miguel Obando y Bravo, although the president acknowledged suggesting him for the job. The Sandinistas, who have refused direct talks with the contras, originally had rejected Obando y Bravo, charging he was sympathetic to the rebels.

In the Dominican Republic negotiations, Obando appeared clearly to support the contra demands. "Now," Arias said diplomatically, "I honestly find that it is not easy for the cardinal, who is not an expert on cease-fires, to be very helpful."

Arias said that "the first step, the most urgent step, the first priority should be a truce."

For the Sandinistas, Arias suggested, more U.S. money to the contras simply provided an excuse for Managua to keep fighting and to delay implementation of the peace plan's provisions for domestic political freedoms.

The administration has asked for $270 million in military aid for the contras in its still-unapproved fiscal 1988 budget. Pending budget passage, it has asked for and received from Congress two separate interim packages of $3.5 million in October and $3.2 million last month in humanitarian assistance. Administration spokesmen have indicated that they plan to request $23 million in nonlethal aid by Tuesday as part of a continuing budget resolution.

The administration and the contras' supporters in Congress have argued that the United States cannot abandon the rebels. They have insisted that without continuing military pressure, the Sandinistas will have no incentive to implement the democratic reforms that they agreed to in the Arias plan.

Responding to that argument today, Arias said he had "no right to question the good faith" of Nicaraguan President Daniel Ortega, who "committed himself to democratize his country" when he signed the agreement.

"Here in Europe," Arias said, "no communist leader has committed himself to democracy. Not even Fidel Castro in 1959. Daniel Ortega did it in August 1987.

"The problem is that as long as there is an aggression, he is going to use it as an excuse. And in a way, he is right. . . . You cannot lift a state of emergency if you are fighting every day."

Asked if he wanted to send a message to Reagan, Arias said, "I have given him so many messages. He knows very well that the contras, from my point of view, are the problem and not the solution."

"The essential disagreement between my position and that of some U.S. officials is precisely that," Arias said. "They still think that supporting the contras is the best way to get the Sandinistas to comply. I believe to the contrary."