WASHINGTON--Soviet Foreign Minister Eduard A. Shevardnadze will come here at the end of the week to discuss prospects for a superpower summit meeting and an agreement to ban intermediate-range nuclear missiles, a U.S. official said yesterday.

The Soviets requested the meeting between Shevardnadze and Secretary of State George P. Shultz, said the official, who spoke on the condition of anonymity.

The official said he could not predict whether a date for a visit by Soviet leader Mikhail S. Gorbachev would be set then. But, the official said, "a scenario for a summit is developing.'

Meanwhile, President Reagan said yesterday that U.S.-Soviet affairs are "a little up in the air" following Soviet leader Mikhail Gorbachev's refusal to pick a date for a summit, but added he still believes a treaty to ban medium-range nuclear weapons is "going to be signed."

"I don't think it was a diplomatic setback, and whether it was a maneuver or not, I wouldn't have an answer to that," Reagan told European television correspondents.

But at the same time, the President acknowledged that "we were hoping they would set a date" for a superpower summit that would bring Gorbachev to the United States for the first time.

"We have said to them, that it's up to them to set a date if they would like to have it, and I have not counted it out as yet," Reagan added. "I don't think that it was a deliberate negative because I think they would have simply said they weren't going to be" attending a summit, he said.

Of the move by the two superpowers to reach agreement on a treaty to eliminate intermediate-range nuclear force weapons, Reagan said, "It seems that our negotiators have eliminated all of the major differences, and there may be a few little details to work out. But we do believe that's going to be signed. Of course, we're a little up in the air right now."

The Secretary of State said the Soviets were making a mistake if they thought their unwillingness to set a date for a summit meeting would produce U.S. concessions.

"The President won't give them something in exchange for a summit that he thinks is unwise from the standpoint of the United States," Shultz said on the "MacNeil-Lehrer News Hour."

Shultz said the U.S. side was prepared to discuss with the Soviets the U.S. quest for a spacebased defense against ballistic missiles.

But Shultz said he could provide no guarantee that the issue would be discussed at the summit.

It was not surprising that the Soviet leader wanted to impose restraints on the U.S. program to develop a defense against ballistic missiles based on advanced technology and nuclear weapons. Gorbachev has maintained that the U.S. Strategic Defense Initiative, known popularly as "Star Wars," would mean extending the arms race into outer space.

But Shultz and his advisers had not expected the Soviet leader to bring up the issue as a barrier to a fall summit, which Gorbachev had agreed to last month after Shevardnadze's talks in Washington with Reagan and Shultz.

"But we are not willing, and I don't think we ever will be willing, to throw in the towel on learning how to defend ourselves," Shultz said.

Earlier, the President had indicated that he had no inclination to be drawn into a battle of wits with Gorbachev over whether the Soviet leader would accept an invitation to visit the United States for a summit meeting.

At the same time, presidential spokesman Marlin Fitzwater said U.S. officials are perplexed by Gorbachev's refusal to set a date for the summit that both sides have contemplated to consumate the INF treaty.

During a picture-taking session with congressional leaders, Reagan was asked if he thought Gorbachev was trying to play mind games with him on the issue of superpower summitry. "If he is, he's playing solitaire," the president replied.