West German officials today welcomed Soviet President Yuri Andropov's offer to destroy some of his country's SS20 rockets as part of a potential compromise in Geneva negotiations on medium-range nuclear missiles in Europe.

Foreign Minister Hans-Dietrich Genscher, speaking in a radio interview, described Andropov's proposal as "a very welcome step by the Soviet Union."

But he also stressed that Soviet insistence on counting British and French nuclear deterrent systems remains the chief obstacle to reaching an agreement before the West begins deployment of new Pershing II and cruise missiles in December.

Moscow has offered to reduce its SS20 arsenal in the European part of the Soviet Union to the same level as the 162 missiles stocked mainly on submarines by France and Britain.

But the United States and its European allies contend that such independent deterrent systems do not fall within the scope of the Geneva talks on intermediate land-based missiles in Europe.

Andropov's latest initiative, however, is perceived by West German officials as an important step because for the first time the Kremlin has acknowledged it would junk some of the SS20 missiles in a potential arms control deal and not just transport them to new sites in Siberia where they could threaten Japan or be moved back to Europe.

The climactic round in the Geneva negotiations is scheduled to open Sept. 6. If no compromise is struck by December, the first nine Pershing II missiles will be deployed in West Germany while Britain and Italy receive consignments of cruise missiles.

Genscher said he is convinced that chief U.S. negotiator Paul Nitze will go into the final round at Geneva with "a high measure of flexibility."

He said that West Germany's top disarmament expert, Friedrich Ruth, will fly to Washington Sunday to assist in formulating the American negotiating strategy for the coming session.

Nitze is also expected to visit Bonn next week to hold last consultations with top West German officials before he returns to Geneva.

In a press conference yesterday, Chancellor Helmut Kohl said he was still optimistic about the chances for a Geneva agreement before the end of the year.

He said that during his vacation in Austria earlier this month he received a letter from Andropov asserting that an arms accord was still possible this year.