VIENNA -- Languidly smoking a cigarette in a carved ivory holder, Alexis Obolensky easily stands out among the pin-striped diplomats who negotiated the European conventional arms treaty. "I have no alter ego anywhere," is how he puts it during a pause from his scrutiny of military minutiae in half a dozen languages.

Chief of the State Department's Russian translation section, Obolensky has spent the past month in Vienna overseeing translation of the accord, to be signed at the Paris summit today. It is the latest in a string of major international documents whose translation he has supervised for the United States, including the Strategic Arms Limitation Treaty, the Conference on Security and Cooperation in Europe and the Law of the Sea.

The 71-year-old Obolensky is master of all six languages in which the Treaty on Conventional Armed Forces in Europe will be signed. Negotiators say he was alone among delegation members to command English, Russian, German, French, Italian and Spanish, and so bore a weighty responsibility in ensuring that the document, one of the most complex treaties in history, would be complete in time for the summit.

The entire six-language text runs around 800 pages. Considered an armistice for the Cold War, it provides for dramatic reductions in battle tanks, armored combat vehicles, artillery, combat helicopters and combat aircraft, and covers territory from the Atlantic to the Urals.

"All of those languages must be letter-perfect and must be something that we can live with for a very long time," says U.S. delegation spokeswoman Elizabeth Prior. "So when someone is looking at it word by word and making sure that in six very different languages it has exactly the same nuance, tone and overt meaning, that is a very difficult task. To have one person doing that in every language is an extraordinary situation."

In addition to providing invaluable linguistic and analytical skills, Obolensky was perhaps the most colorful figure among the envoys and weapons specialists assembled at the Hofburg palace, where the treaty was negotiated over the past 20 months.

His official re'sume' begins by noting that his family history can be traced to the 9th century. A descendant of the Rurik dynasty, which ruled Russia for centuries before the Romanovs, Obolensky is a would-be prince. Members of some foreign delegations deferentially refer to him as such.

Jeweled rings on his fingers, Wedgwood cuff links on his shirt and a gold watch chain slung across his chest, Obolensky recounts over coffee near the Hofburg the evolution of his mutilingual proficiency. "I was born bilingual," he says. "I don't remember which language I spoke first, Russian or German."

Conceived in Russia during the bloody aftermath of the 1917 revolution, he was born in Germany after his pregnant mother and his father, a member of the regimental guard of Czar Nicholas II, fled from the Bolsheviks. His paternal grandfather, a deputy foreign minister, helped draft the 1905 October Manifesto, which resulted in the first Russian constitution. His father, Nicholas Obolensky, opted for escape to Heidelberg after involvement in an abortive plot to free the czar and his family from Bolshevik captors, who assassinated them.

"They got to Yekaterinburg, to Sverdlovsk, one day or two days after the execution. ... It was all over." The Communists sentenced Nicholas Obolensky to death in absentia.

Have Kremlin delegations been aware of his background during the 45 years Obolensky has worked in Soviet affairs? "They have without exception, even at the worst times of the Cold War, always treated me with a certain respect and a certain deference, not due to my person but due to the family standing. That is true to this day," he says. "... If you want a flippant answer, I think that's the way it ought to be."

High-level Soviet authorities have sought him out because of his family background, he recalls. While working as the Department of Commerce's chief specialist on Soviet fisheries from 1968 to 1973, Obolensky says he was "besieged" with personal questions. At one official reception, members of the Soviet delegation suddenly "came over and shook hands with me. I asked why, and they said, 'We want to touch the hand of a real Ruriki.' "

He learned English from a British governess. And "my grandmother, as all people of that generation and that class in Russia, could not fancy anybody not speaking French, so I spoke French. I have no memory or reminiscence of myself without speaking French."

Flawless Italian came in the course of a 34-year residency in Italy, where he earned a doctorate in international law at the University of Rome and headed the Russian broadcasting section of Italian state radio after World War II. Obolensky married a lieder singer from Alabama whom he met in Florence. They then moved to the United States, where he took American citizenship in 1963. "Remember Cary Grant? I'm not as handsome as he is, but he was a war bride and so was I."

Italy's chief delegate to the Conventional Forces in Europe talks, Paolo Pucci, says Obolensky embodies the linguistic traditions of the pre-revolutionary Russian upper class. "The good habits of the past were preserved by Prince Obolensky," says Ambassador Pucci. "He's perfect. His Italian is better than mine."

What's more, Obolensky is also fluent in Dutch, Latin and classical Greek.

Of the task of rendering the Treaty on Conventional Armed Forces in Europe into five tongues from the English in which it was negotiated, he says, "No language is translatable verbatim into another language. And therefore when one deals with other language versions, the problem that arises ... is how to give as close a possible verbatim version of the other language texts without biasing the substance and the sense."

He says translation of the accord proceeded without major hitches. This was done with the assistance of three other State Department linguists under his direction and in consultation with Soviet translators and representatives of the other 20 nations that were party to the accord.

Glasnost, to which the Vienna talks owed their swift pace, positively influenced the Soviet attitude to translation as well. In previous talks, "even after Gorbachev," Obolensky says, "it was pretty much hard-nosed, unyielding and hostile, unwilling to hear possible differences. And I'm not talking about substantive differences. I'm talking about purely linguistic differences." He says he was inclined to believe that discrepancies in the Russian texts of earlier treaties were "ill-intentioned" moves aimed at circumvention.

Despite the transformations in the Soviet Union, the State Department's watchful Rurik vows, "the carefulness of the review of the text remains. It has nothing to do with the political atmosphere. What does change is that the differences, not to say discrepancies, that I've found in the Russian version have been settled here with this treaty with absolutely no problem."