Secretary of State George P. Shultz said yesterday he welcomed the Soviet Union's proposal for a 50 percent cut in strategic offensive weapons. But Shultz warned again that President Reagan will not abandon research and testing of his Strategic Defense Initiative in exchange for progress in the Geneva arms talks.

In separate television interviews, Shultz and Assistant Secretary of Defense Richard N. Perle stressed that Reagan was sincere in saying he will not use SDI, also known as "Star Wars," as "a bargaining chip."

The United States, they said, considers it urgent to continue SDI research. They empasized that the administration reserved the right to conduct the kind of testing permitted by the 1972 Antiballistic Missile Treaty (ABM).

However, their remarks contained a hint that there might be some give in the U.S. position on testing.

"Any deal on research would be ridiculous because there is absolutely no way to verify if it's being observed . . . . The president is not going to give it up," Shultz said on NBC-TV's "Meet the Press."

But when asked about testing and development of space weapons, Shultz was less vehement: "What we are doing is within the framework of the ABM%) treaty, which does not prohibit certain kinds of testing."

Similarly, Perle, interviewed on CBS-TV's "Face the Nation," said, "There's no way [Reagan] will agree to limits on research." It was not clear whether his failure to mention testing was deliberate.

Shultz and Perle also acknowledged that the administration was uncertain about the extent to which the Soviet proposal would encompass large land-based intercontinental missiles. Such weapons are the core of Moscow's nuclear force.

In a White House meeting Friday, Soviet Foreign Minister Eduard Shevardnadze gave Reagan a letter from Soviet leader Mikhail Gorbachev broadly outlining the arms-control proposal that the Soviets will present at the Geneva arms talks this week. U.S. and Soviet officials have refused to disclose details of the proposal.

However, a senior U.S. official said yesterday that Shevardnardze left the impression that Moscow wants to base the 50 percent reduction on strategic nuclear "charges," including missile warheads, nuclear bombs, short-range attack missiles aboard bombers and other weapons capable of striking Soviet or U.S. territory.

Without further "sublimits" on particular weapons, such a proposal would do little to cut Moscow's arsenal of heavy land-based missiles.

That concern was alluded to by Perle, who noted that the Soviet proposal could turn out to be a throwback to ideas advanced by the Soviets in the 1970s and rejected by the United States as propaganda ploys.

Asked about Perle's comment, Shultz replied, "I don't know whether it's a step backwards or forwards . . . . We have to see what's being talked about. But if the proposal is to go back to the idea that all warheads are the same -- that's what Mr. Perle was talking about -- I agree with him."

However, Shultz rejected suggestions that the Soviet proposals should be written off as propaganda. He counseled a wait-and-see approach.

"What's new is that they have brought forward a proposal, or will in Geneva tomorrow, that deals with offensive matters," he said. "To date, they haven't done that before. We welcome that.

"We're not trying to project optimism or pessimism," Shultz continued. "We're trying to project realism . . . . We have proposals on the table. Apparently the Soviets will put some proposals on the table on Monday or Tuesday. We welcome that, and will see where we go from there."

Shultz also referred to the White House visit today of Jordan's King Hussein and the administration's intention, announced Friday, to sell Jordan as much as $1.9 billion worth of arms.

Concerning Hussein's proposals for possible peace talks with Israel, Shultz said the king was right to insist that any Jordanian negotiating team have Palestinian representation.

But, in what appeared to be a strong reaffirmation of the U.S. refusal to deal with the Palestine Liberation Organization, Shultz added: "What their the Palestinians' status is in regard to the PLO is a big question mark. To the extent that the PLO remains dedicated to armed struggle -- and so far as I can see, they do -- they don't belong at the bargaining table.