LOS ANGELES, AUG. 29 -- President Reagan said today that the United States and the Soviet Union are "close to an agreement" on the elimination of intermediate-range nuclear missiles.

Reagan said that while he is optimistic about chances of a superpower accord on these ground-launched missiles, it also is a "particularly good time" for the Soviets to renounce military adventurism around the world.

"They can stop helping the Sandinista regime in Nicaragua subvert their neighbors," Reagan said in his weekly radio address, delivered from his penthouse hotel suite before he returned to his ranch near Santa Barbara, Calif.

"If the world is to know true peace," he said, "the Soviets must give up these military adventures."

Reagan said he had proposed the global elimination of intermediate-range missiles, and added, "Today, we're close to an agreement with the Soviets to do just that."

Delivering the Democratic response, Sen. Carl Levin (Mich.) also spoke of the intermediate-range nuclear force (INF) issue, saying, "President Reagan should be commended for his efforts to achieve a verifiable INF treaty, and I hope such an agreement can be concluded in the weeks ahead.

"But while this INF step is an important one, it is also a small one," Levin added. "Keep in mind that the superpowers together have over 50,000 nuclear warheads. The INF agreement would eliminate only about 4 percent of that total . . . . With or without an INF agreement, the superpower nuclear arms race will continue."

Chief U.S. arms negotiator Max M. Kampelman, in an interview taped for the syndicated television show "John McLaughlin: One on One," voiced optimism that the two sides might be able to reach agreement on a 50 percent reduction in long-range, or strategic, weapons, by year's end.

"I think it's doable, and I cannot see why we shouldn't be able to come up with an agreement if the Soviets will join us in working for that agreement," he said.