The French government acknowledged today that for the past seven years it has been in possession of information showing that former U.N. secretary general Kurt Waldheim hid details about his wartime service.

The French disclosure marked the first confirmation that Waldheim's controversial activities as a German officer in World War II stirred the curiosity of a western government while he was at the United Nations from 1971 to 1981. It coincided with an assertion that Soviet military authorities in Vienna knew that Waldheim was wanted as a war criminal by Yugoslavia as early as 1948.

The former U.N. chief is widely regarded as the front-runner in Sunday's decisive round of the Austrian presidential election despite allegations that he must have known about Nazi war crimes in the Balkans and the mass deportation of Jews. He is supported by the conservative People's Party, which is seeking to capture the presidency from the rival Socialists.

Today's French statement was prompted by claims by the Simon Wiesenthal Center of Los Angeles that the French, West German and Austrian governments sought to check details of Waldheim's biography during the 1970s. The West German and Austrian governments have said they are investigating the allegations.

The French government today released portions of its own biographical file on Waldheim, compiled in 1979 by French military officials in West Berlin on the basis of Allied archives. The file recorded that Waldheim was assigned to a German unit in the Balkans headed by Gen. Alexander Loehr, who was later executed for war crimes, from 1942 to 1944.

In a biography published in 1977, the former U.N. chief claimed that he was a law student in Vienna during this period and omitted all reference to his service in Yugoslavia and Greece.

The head of the Simon Wiesenthal Center, Rabbi Marvin Hier, said that today's French statement was unsatisfactory because it did not reveal why Paris became interested in Waldheim in 1979 or who ordered the inquiry.

"Someone was suspicious of Kurt Waldheim," he said in a telephone interview from the Netherlands. "If this is the French government's final word on this matter, then I am sorry to say that they have something to hide."

A spokesman for Prime Minister Jacques Chirac said in Paris that the French government still had not been able to establish who ordered the report. Former president Valery Giscard d'Estaing, who was in office when it was compiled, has said that he was unaware of its existence.

Jewish groups in the United States and Western Europe have suggested that Waldheim's wartime record could have made him vulnerable to blackmail by intelligence agencies in the East. Waldheim has denied knowledge of war crimes attributed to Loehr, including the mass deportation of Jews from Greece and reprisals against Yugoslav civilians following attacks by communist partisans on German troops.

The World Jewish Congress, Waldheim's chief accuser, said Friday its researchers had found captured Nazi documents in the National Archives in Washington showing Waldheim conveyed to his superiors a German Army division's request for the seizure and deportation of Greek civilians in 1943, United Press International reported. The request was subsequently approved.

In Vienna, a Waldheim spokesman said, "We haven't seen the document; therefore we cannot give an answer."

The former head of the Yugoslav military delegation in Austria said today that he had passed on a list of alleged Austrian war criminals, including Waldheim, to a Soviet general in early 1948. Waldheim was then working as an Austrian official in Soviet-occupied Vienna.

In a telephone interview from Belgrade, Anton Kolendic said that he did not know what use the Soviets made of the information because relations between Yugoslavia and the Soviet Union deteriorated a few months later. He identified his Soviet counterpart as a Col. Gonda who, he said, knew Yugoslavia well after having served on a military mission to the Yugoslav partisans.

"We gave the Soviets the entire documentation on Waldheim that was later given to the United Nations," said Kolendic, explaining that this was normal procedure.

Kolendic denied remarks attributed to him in a Belgrade bimonthly magazine, Duga, that an attempt had been made to recruit Waldheim as a spy. During the immediate postwar period, former Nazis were recruited by both western and eastern powers as potential intelligence assets.

The former Yugoslav official said Waldheim was among 25 to 27 Austrians wanted by the Yugoslav war crimes commission. For reasons that have never been made clear, Yugoslavia dropped its investigation into war crimes allegedly committed by Waldheim.

The Belgrade daily Vecherni Novosti, meanwhile, quoted a retired Yugoslav captain as saying Waldheim attended talks on the surrender of German troops in northern Yugoslavia in May 1945. Waldheim has repeatedly said that he was in Trieste at the time.

The newspaper quoted Milan Skero, a former interpreter for the partisans, as saying that he met with Loehr and Waldheim on May 7, 1945.

In the first round of the Austrian presidential election in April, 49.6 percent of the vote went to Waldheim and 43.7 percent to his Socialist opponent, Kurt Steyrer.

As the generally restrained campaign came to a close, Steyrer's supporters stepped up their criticism of Waldheim. A packed election meeting in Vienna last night heard intellectuals depict Waldheim as a "professional opportunist" who had lied about his past.

Waldheim's supporters, meanwhile, published a full-page advertisement in most Austrian newspapers appealing to "the decency and fairness" of the nation and urging Austrians to vote for him Sunday.