WASHINGTON--Prospects for a superpower arms deal appeared to brighten yesterday with word from a Kremlin spokesman that the Soviets may ease their stand on "Star Wars" testing and the disclosure that Soviet leader Mikhail Gorbachev sent an upbeat message to Washington.

"We have not cut off our dialogue," said Georgy Arbatov, a Kremlin adviser who took part in marathon arms negotiations at the October 11-12 summit in Iceland. "If the President needs some face-saving devices, we can find him some."

The negotiators in Iceland broke off in exhaustion and acrimony over President Reagan's refusal to accept Gorbachev's demand to amend the 1972 Anti-Ballistic Missile Treaty to bar Star Wars research and testing outside the laboratory.

"There can be qualification" of the laboratory demand, Arbatov said on the CBS program "Face the Nation."

Secretary of State George P. Shultz said Gorbachev sent a verbal message through diplomatic channels after the summit urging Shultz to meet next month in Vienna with Soviet Foreign Minister Eduard Shevardnadze.

"The main message seemed to be that Shevardnadze and I had developed a certain relationship and we should keep it moving. And we should be thinking about when we might meet again," Shultz said on NBC's "Meet the Press."

Neither the Soviet nor the U.S. officials indicated that a Soviet order on Sunday expelling five American diplomats from the Soviet Union would hamper arms control talks.

"We will protest and we will take some action," said Shultz, but the exact response "remains to be seen." The latest expulsion appeared to be a Kremlin retaliation to the U.S. order that 25 xlleged Soviet spies employed at the United Nations leave the United States.

In a statement that mirrored Arbatov's optimism on arms talks, White House chief of Staff Donald H. Regan said Soviet diplomats in Geneva were shifting their stand on Star Wars, known formally as the Strategic Defense Initiative.

While "there has been no letter from Mr. Gorbachev to the president since Iceland," Regan said, "there have been hints delivered to some of our negotiators that perhaps they could discuss further the SDI and its testing."

The comments by Arbatov, Shultz and Regan reflected a more optimistic outlook expressed by Soviet and U.S. officials in the days since the Iceland meeting broke up with acrimonious finger pointing as each side blamed the other for the impasse.

Arbatov repeated some Soviet arguments against Star Wars, which envisions exotic weapons such as lasers to knock down ballistic missiles as they sail through space.

"I think all of this...is a bit irrational," said Arbatov, explaining that the United States would not need strategic defenses if it accepted Gorbachev's proposal to eliminate all nuclear weapons by 1996.