The Soviet Union "showed some forward movement" during the latest round of long-range or strategic arms reduction talks (START), but no breakthrough will come until Moscow sees what happens in the companion talks over medium-range missiles in Europe, U.S. START negotiator Edward L. Rowny said yesterday.

"We can't make any real progress," Rowny said of his discussions, until an agreement is reached in the talks on intermediate-range forces (INF) or the first U.S. Pershing II and ground-launched cruise missiles are deployed as scheduled this winter in western Europe.

Rowny, who held a news conference at the White House after reporting to President Reagan, said the Soviets kept bringing up the medium-range missiles in the talks on the longer-range weapons because the longer-range weapons are "not their priority." Instead, their preoccupation is to prevent the Pershing and cruise deployments, he said.

In Moscow, according to United Press International, Soviet President Yuri V. Andropov charged that the United States had brought the Geneva talks "practically to a standstill" and that the planned U.S. missile deployments may cause "a very dangerous situation" for the people in Europe.

Andropov's remarks came in a statement released by the Soviet press agency Tass after the Soviet leader met with Portuguese Communist Party General Secretary Alvaro Cunhal.

At one point in his news conference, Rowny said the Soviets told him they could not make the strategic missile reductions they already had proposed "if there are deployments in Europe" of American missiles.

Asked about European suggestions that the strategic and medium-range missile talks be merged, Rowny said such talk was "premature." He also said that if the INF negotiations failed, merged talks would take place only with some new American missiles deployed in Europe.

Rowny opened the 20-minute session with a statement that called the latest round of talks the "most significant" to date.

He said he was "hopeful" that some agreement could be reached eventually.

On July 8 he had presented the Soviets with a complete text of a draft treaty, he said. He described that text as responsive to some of the basic Soviet objections to earlier U.S. proposals.

The Soviet negotiators responded with "some flexibility" of their own. But their flexibility "was in non-central issues," he said, and thus "not in the same spirit as ours."

As an example, Rowny said the Soviets remained "very much opposed to reducing the large destabilizing systems" of land-based missiles, as the United States has proposed.

Although the Soviets said they would "limit the total number of weapons," he said, they won't say what number they have in mind.