WASHINGTON — Defense Secretary Caspar W. Weinberger on Tuesday "officially confirmed" that the Soviet Union has deployed a new mobile nuclear missile, the SS-25, and called it "an unquestionable violation" of the second strategic arms limitation treaty that creates fresh doubt on the chances of achieving a new arms control pact.
"Recent history shows that arms control has hardly been a raving success," Weinberger warned, speaking less than a month before President Reagan and Soviet leader Mikhail S. Gorbachev are to meet in Geneva.
"It is difficult to argue that the only moral course of action open to the United States is more of the same," he said. "There is nothing moral about a situation in which the strength of the democratic nations is slowly eroded."
'Stunning . . . Hypocrisy'
Accusing the Soviet Union of "a stunning degree of hypocrisy" in opposing Reagan's Strategic Defense Initiative to develop a defense against nuclear missiles, Weinberger said: "Real arms reduction agreements with the Soviets are so difficult" because "the moral foundations of our two governments" collide.
Weinberger's comments, in a speech before an Ethics and Public Policy Center conference, were his most recent--and in some ways, his strongest--in a series of statements defending the basic aim of the Reagan initiative and warning against any move to scrap the controversial space defense plan in exchange for arms reductions by the Soviets.
Administration critics have charged that SDI, popularly called "Star Wars," will block any new arms control efforts because Moscow probably would want to build more offensive weapons in order to overwhelm a defensive system.
But Weinberger insisted: "We don't think that there is any real contradiction between serious arms reduction negotiations and vigorous research into strategic defense. In fact, the efforts are completely complementary."
To bolster his case, the defense secretary announced that the United States has independently confirmed a development that officials have talked of unofficially for almost a year: the deployment of a new Soviet intercontinental nuclear missile, the SS-25.
"I can, today, officially confirm that one (type) of their new ICBMs, the mobile SS-25, is now being deployed and is an unquestionable violation of the assurances given to us under the SALT II accord," he said. "This single-warhead missile . . . is very accurate. It is road-mobile and can be housed in launcher garages equipped with sliding roofs. This makes it an extremely versatile weapon and a very dangerous weapon."
Number Deployed Not Disclosed
A Pentagon spokesman later said he was unable to say how many SS-25s the Pentagon believes have been deployed or whether there is any evidence that the Soviets are retiring older missiles as they begin deploying new ones.
State Department officials said late last year that they had detected signs of SS-25 deployment. The Soviet Union informed the United States that it was deploying the missiles earlier this year, officials said. But Weinberger's statement was the first high-level public charge from the Reagan Administration that the missiles were operational.
Other officials said the deployment of the SS-25 came as no surprise and did not alter the arms control landscape. "It's been expected for a long time," said Paul H. Nitze, Reagan's special adviser on arms control.
Nitze and other officials said that the SS-25 violates the 1979 SALT II treaty because the pact permits each country to deploy only one new type of ICBM and Moscow has already designated another missile, the SS-X-24, as that new type. The Soviets assert that the SS-25 is merely a modernized version of an existing ICBM--the SS-13--which would be permitted under the treaty, but U.S. officials reject that argument.
"It doesn't look anything like the SS-13," Nitze said.
Treaty 'Fatally Flawed'
The SALT II treaty, signed during the Administration of President Jimmy Carter, never has been ratified by the United States, in part because Reagan and other conservatives attacked it as "fatally flawed." Nevertheless, Reagan has said that he will observe the treaty's provisions and has criticized the Soviets for allegedly violating them.
On another arms control front, Nitze and State Department legal adviser Abraham Sofaer told members of Congress that "Star Wars" research will remain within the bounds of a traditional interpretation of the 1972 anti-ballistic missile treaty, even though the Administration believes that interpretation is mistaken.
"Our SDI research program has been structured and, for solid reasons, will continue to be conducted, in accordance with a restrictive interpretation of the treaty's obligations," Nitze told a subcommittee of the House Foreign Affairs Committee.