The Soviet Union has stolen the disarmament show with a dramatic invitation to U.N. leaders to witness the destruction of intermediate-range nuclear missiles on its soil next month.

Soviet Foreign Minister Eduard A. Shevardnadze, speaking Wednesday at a U.N. disarmament session, asked Secretary-General Javier Perez de Cuellar, members of the Security Council and representatives of the 102-nation non-aligned movement to come to the missile bonfire in July. It will be "not the Bolshoi Theater, but a major premiere nonetheless, a momentous, historic event," he declared.

"When the first public execution of weapons in human history takes place, no one is likely to cry or weep. It will herald an end to a lot of tears," he said. "But having dug a grave for weapons of mass destruction, mankind must now build the foundation of a nuclear-free and non-violent world."

Diplomats said Shevardnadze's speech was a tour de force that put the United States on the diplomatic defensive.

Even U.S. Ambassador Vernon A. Walters praised the speech as "hopeful, useful and good."

"It was an extremely interesting new speech, it broke a lot of new ground and it is deserving of study," he said. Secretary of State George P. Shultz plans

to deliver a U.S. statement before the 40-nation conference next week.

But diplomats speculated that Vice President George Bush, or even President Reagan, might make a last-minute decision to offset the Soviet first-strike advantage and deliver a weighty American rejoinder.Meanwhile, at Mutlangen, West Germany, American officers showed how a Pershing-2 missile that would take ten minutes to deliver the equivalent of two Hiroshima atomic bombs to the Soviet Union will take three years to dismantle.

Preparations are now under way at the American base, which houses a battalion of Pershing-2s, for the missiles' eventual destruction under the superpower Intermediate-range Nuclear Forces treaty, which came into force last week.

To demonstrate how the treaty will work in practice, the U.S. Army on Wednesday drove a group of reporters into the heart of the normally top-secret base - one of three in West Germany where a total of 120 Pershing-2s are stationed.

Teams of up to 10 Soviet inspectors can make three visits to the West German bases before the end of September to check numbers and data given in the pact.

The Soviet inspectors may even spend the night with the Pershings.

U.S. officials said the officials would be billeted in a small one-story guard block in the center of Mutlangen base if they chose to spend their full 24-hour visiting time on site.