LOS ANGELES, AUG. 26 -- President Reagan today welcomed West Germany's willingness to destroy its Pershing IA missiles, saying that the decision paved the way for the United States and the Soviet Union to "wrap up an agreement on intermediate-range nuclear missiles promptly."

Reagan praised the action by West German Chancellor Helmut Kohl in a speech on U.S.-Soviet relations in which he also called upon the Soviet leadership to demonstrate its proclaimed commitment to openness by publishing its military budget, allowing free debate, tearing down the Berlin Wall, withdrawing from Afghanistan and accepting self-determination in Eastern Europe.

A senior official who briefed reporters before the speech said prospects for a treaty that would remove medium-range and short-range nuclear missiles from Europe and Asia were now "very promising" as a result of Kohl's action and a new U.S. position calling for less stringent verification.

Kohl said in Bonn that the 72 aging Pershing IA missiles, which have U.S.-owned nuclear warheads, "will not be modernized, but rather destroyed" if the U.S.-Soviet treaty scrapping the other missiles is approved and implemented.

In his speech to the Town Hall of California, which was also beamed by satellite to a U.S.-Soviet conference in Chautauqua, N.Y., Reagan said that Kohl had removed the "artificial obstacle" of the Pershing IAs from consideration.

"We are therefore hopeful that the Soviet Union will demonstrate that there is a substance behind the rhetoric they have repeated so often of late -- that they genuinely want a stabilizing INF {intermediate-range nuclear force} agreement," Reagan said. "If so, they will move to meet our proposals constructively rather than erect additional barriers to agreement."

White House officials said an aide to Kohl had given national security adviser Frank C. Carlucci a day's notice of the West German proposal. The aide called Carlucci in Santa Barabara on Tuesday morning, and the national security adviser briefed Reagan on the helicopter ride from the president's mountaintop ranch to the Los Angeles hotel where he spoke today.

The senior official who briefed reporters said there was "absolutely no pressure from the United States" on the West German government to make a decision on the Pershings. But he said Reagan was pleased by Kohl's "gesture" and had expressed his gratitude in an exchange of letters with the chancellor.

Reagan's speech today mixed measured praise of reforms initiated by Soviet leader Mikhail Gorbachev, whom he did not mention by name, with repeated challenges to the Soviet leadership to expand its policy of "glasnost," or openness.

"I say to the Soviet leadership it is time to show some glasnost in your military affairs," Reagan said. "First, publish a valid budget of your military affairs -- just as we do. Second, reveal . . . the size and composition of the Soviet armed forces. Third, open for debate in your Supreme Soviet the big issues of military policy and weapons -- just as we do."

The president traced the history of U.S.-Soviet relations from the World War II conference of allied leaders at Yalta, which he said "produced tangible diplomatic results," including assurances of self-determination for the peoples of Eastern Europe. Within months, Reagan said, Soviet leader Josef Stalin had broken the promises made at Yalta, ushering in an era of Cold War conflict.

But Reagan said recent world developments, including economic reforms and democratic changes in such nations as South Korea, China and the Philippines, had signaled "exciting new prospects for the democratic cause."

"Perhaps, then, we may finally progress beyond the postwar standoff and fulfill the promises made at Yalta but never acted upon," Reagan said. "Perhaps, it is not too much to ask for initial steps towards democratic rule and free elections."

{"The president reiterated U.S. commitment to the doctrine of neo-globalism that envisages interference in the internal affairs of sovereign countries and accused the Soviet Union of showing all too little real willingness to move towards peace," the official Soviet news agency Tass said in a report on Reagan's speech, United Press International reported.

{"Reagan again made it clear that the U.S. wishes to keep the problem of American nuclear warheads for Pershing IA missiles outside the framework of the Geneva talks. Judging by President Reagan's speech, the U.S. should not make any special effort in this situation, only put forward demands and go with its present-day policy without changing it in any way," Tass said.}

Reagan, for the most part, avoided the harsh rhetoric he used early in his first term, when he described the Soviets as "the focus of evil" and "the evil empire."

But he continued to be sharply critical of Soviet actions in Afghanistan and Nicaragua. Restating the "Reagan doctrine" of assisting democratic insurgents opposing communist regimes, he called the policy "a matter of conscience" for the West.

"The fact remains that, in Afghanistan, Soviet occupation forces are still waging a war of indiscriminate bombing and civilian massacre against a Moslem people whose only crime is to love their country and their faith," Reagan said. "In Central America, Soviet-bloc arms deliveries have been speeded up during the past year . . . by more than 100 percent. So while talking about reforms at home, the Soviet Union has stepped up its efforts to impose a failed system on others."

On another topic, Reagan said Washington and Moscow "have found a parallel interest" in ending the Iran-Iraq war. But the official who briefed reporters said "we should not read a lot into this because it does not really disguise the conflict of aims in that region."