West German Chancellor Helmut Kohl and British Prime Minister Margaret Thatcher stressed today their desire to mark the 40th anniversary of the end of World War II as the birth of a new era of peace and freedom rather than the defeat of the Axis powers.

The two leaders, speaking at a joint press conference after consultations here today, said there were no plans for international ceremonies on May 8, the date of the Nazi surrender 40 years ago, that would serve to distinguish the victorious wartime allies from the vanquished nations of Germany, Italy and Japan.

The West German government has insisted that it wants to avoid any repetition of the embarrassment felt last year when Kohl was rebuffed after seeking to be included in June ceremonies commemorating the 40th anniversary of the Normandy landings.

Bonn is also troubled by the possibility that the Soviet Union might exploit the May anniversary to intensify propaganda attacks against West Germany. Moscow has accused the Kohl government of trying to reclaim territories in Eastern Europe that were lost in the war.

Earlier, the West Germans were troubled by rumors that the May anniversary might provide an occasion for a summit in Berlin between President Reagan and Soviet President Konstantin Chernenko. Senior advisers to Kohl said they feared that such a meeting would be a painful reminder of the superpowers' rule over a divided Germany, but they were reassured by Reagan administration officials that a Berlin summit had been ruled out.

Asked today if there might be any official gathering of wartime allies, including the Soviet Union, to mark the May anniversary, Thatcher said, "I doubt it. I think each of us would wish to remember that day in his or her own way."

The prime minister, who reversed an initial decision by her government not to hold any official end-of-the-war ceremonies following heated protests from veterans' groups, said it was still not clear what form the British commemoration would take.

"We shall approach the anniversary in a spirit of commemorating 40 years of peace and freedom, because we believe that year saw a new birth of freedom," she said.

Kohl told reporters he had explained to Thatcher the special psychological pressures faced by West Germany, which regarded May 8, 1945, as "a day of liberation from barbarism."

But the chancellor emphasized that the real triumph to be celebrated this May is "the great historical achievement of maintaining peace and freedom in the West over the past 40 years."

Kohl confirmed that leaders of the seven top industrialized nations would salute this theme in a declaration when they meet in Bonn from May 2 to 4, only days before the sensitive war anniversary.

The West German leader said a subdued observance of the end of the war was proper because even though it was "a day of liberation" for most Germans, "we cannot forget the suffering and deaths of the victims in this war."

He said West Germans should treat the occasion in a spirit of "remembrance and self-examination."

Kohl plans to attend a somber remembrance of the war with Jews in West Germany at the site of the Bergen-Belsen death camp on April 21. He has also proposed an ecumenical service in the massive Gothic cathedral in Cologne, one of the cities most devastated in the war.

On other subjects, Kohl and Thatcher said they discussed East-West relations and expressed cautious optimism about the prospects for nuclear arms control following this month's Geneva agreement by the United States and the Soviet Union to start new negotiations on strategic arms, medium-range missiles and space weapons.

She said that the determination and strength of the British and West German governments to proceed with the deployment of cruise and Pershing II missiles paid off in persuading the Soviet Union to return to the arms talks.