Vienna — A new page has just been added to the ''Wallenberg mystery.'' This is the case of the Swedish diplomat who saved thousands of Hungarian Jews from Hitler's death camps - and then disappeared in Soviet-liberated eastern Hungary.
Although almost 40 years have passed, it still is a sensitive and embarrassing issue for the Soviets. They have coldly brushed off repeated Swedish attempts to learn more about his fate.
In 1957, they asserted that Raoul Wallenberg had died 10 years earlier in Moscow's Lubyanka prison. But reports surfacing periodically since then suggest he lived on at least into the early '70s.
Now, according to recent information from Budapest, the Soviet leadership has vetoed a Hungarian move to restore a statue commemorating Wallenberg to its originally intended site in the Hungarian capital. The statue was commissioned soon after the war, but it disappeared on the eve of its unveiling - to reappear in altered form in the town of Debrecen, in eastern Hungary.
The statue's restoration to its former location in Budapest was first suggested in January in a review of the Hungarian Historical Society, which urged that it be returned next year. That will be the 40th anniversary of Wallenberg's disappearance while on his way in January 1945 to the seat of the newly created Hungarian provisional government at Debrecen, where Soviet Army headquarters were also located.
That journey was the last the outside world was to see of Wallenberg.
Official Hungarian approval of the proposal to restore the statue was evident in Budapest's Magyar Nemzet, the newspaper of the communist-led Patriotic People's Front. The newspaper hailed it as a ''worthy gesture'' of remembrance.
Official acquiescence may have been encouraged by the recent advance in relations between Budapest and Stockholm, due in part to the growing economic cooperation between Hungary and Western Europe. But there seems to be no doubt about Budapest's genuine regard for Wallenberg and his record.
Apparently, the Hungarians presumed that, since they were in no way responsible for what happened to him in the Soviet Union after the war, there could be no objection from that quarter to their wish to do belated justice to his memory.
Events have proved them wrong. When Magyar Nemzet's article appeared last March, sources in Budapest say, the Russians lost little time in making the Hungarians aware of their disapproval.
They did so not by way of formal diplomatic demarche or protest, but through party channels, i.e., through the contacts maintained between the apparatus of the Soviet Communist Party and all the party committees of Eastern Europe. It is through such channels that Moscow's influence is brought to bear on all decisions made by its allies in sensitive policy questions.
Even official Hungarian accounts still tend to obscure precisely what happened to the original Wallenberg statue - a 90-foot-high bronze in ''St. George and the dragon'' style on a granite plinth.
It stood briefly in Budapest's St. Stephen's Park - site of the former Jewish ghetto - in the spring of 1949. But on the very eve of the official unveiling, it simply disappeared. Some people who claimed to be eyewitnesses said it was removed by the Russians and badly ''damaged'' in the process.
Since 1953, a much-modified version of the statue has stood in the little town of Debrecen, which was Wallenberg's destination when he was picked up by the Russians. The Debrecen statue is a standard anti-Fascist memorial. There is no trace of the character intended in the original sculpture, nor does the original's inscription of ''undying gratitude'' to Raoul Wallenberg appear.
But however much its meaning might have been lost in this substitute version, the older Hungarian generation's regard for Wallenberg clearly remains.
''It is time to honor him for what he did,'' an official source commented recently to a Western journalist.
Ever since the 1956 uprising, the Budapest leaders have combined domestic reform with an understandable political prudence in their relations with Moscow and with fellow members of the Warsaw Pact.
For example, Budapest has been careful not to openly identify with either the persistent endeavors of the Swedish government to persuade the Russians to throw light on Raoul Wallenberg's fate or with the support given those efforts by the United States and other Western countries.
(Those latter efforts have included President Reagan's step in 1981 of making Raoul Wallenberg an honorary US citizen - Winston Churchill is the only other foreigner to be so honored. Secretary of State George Shultz also raised the issue with Andrei Gromyko at the opening of the Stockholm conference in January.)
Privately, nonetheless, the Hungarians have left Swedish and other diplomats with little doubt of their feeling for the young diplomat who, for six months in 1944, was responsible for saving the lives of as many as 100,000 Hungarian Jews.
He daily exposed himself to great danger, snatching Jews to safety from under the very noses of the Nazis and their domestic Hungarian Nazi Party. He provided many with Swedish passports and forged documents.
Others he protected in ''safe'' Swedish houses until they could be taken out of the country.
His activities were supported by funds from the American Joint Relief Organization and other US agencies. In Soviet eyes, this was probably enough to make him suspect of being something more than a humanitarian, neutral diplomat.
It could be that, given the current state of East-West relations, the Russians are going to do nothing that might seem to be a concession to the US or to the West as a whole, even on a humanitarian issue.
In the process, the more generously inclined Hungarians have apparently been snubbed, and the statue of Raoul Wallenberg seems destined to stay in its provincial obscurity at least for some time to come.