Alexander Shalnev, the White House correspondent for the Soviet news agency Tass, stands to the side of the briefing room and watches a form of discourse he is unlikely to encounter in the Kremlin. UPI's Helen Thomas is crossing swords with presidential press secretary Larry Speakes. Thomas parries by challenging Speakes' "sinking" credibility, and Speakes strikes back with "What kind of garbage are you talking about, Helen?"

A wicked Bill Buckley grin cuts across Shalnev's face. He is a Russian version of a 38-year-old prep. He wears loafers, pleated flannel slacks, a gold-buttoned blazer and a red wool tie. Not a single polyester fiber touches his body. Shalnev seems more like a visiting free-lancer from Private Eye or Punch than a servant of the Union of Soviet Socialist Republics.

"This is bloody hilarious," he says as Thomas and Speakes continue their weird fandango.

When Speakes announces that four Soviet journalists will interview the president in the Oval Office later that day, it comes as no surprise to Shalnev. That interview, which appeared in yesterday's editions of the Soviet newspaper Izvestia, was the first such session since Nikita Khrushchev's son-in-law, Alexei Adzhubei, spoke at length with John F. Kennedy in 1961. Shalnev was the intermediary between the Kremlin and the White House.

Veterans in the White House press room remember Shalnev's predecessor -- a hulking figure in somber suits and heavy homburgs. But no one, including Shalnev, remembers his name.

"He was a big, beefy stereotype of the Russian correspondent," says Thomas. "He was almost square. He was Khrushchev with hair." For once Speakes agrees with Thomas: "He looked like one of the guys you used to see standing on top of Lenin's tomb for parades before Gorbachev came along."

"I think his name was Boris," says ABC's Sam Donaldson. "At least he looked like a Boris. He was built like a refrigerator. I'd try to get a rise out of the guy and tell him 'Get out of Afghanistan,' but he'd never respond."

Shalnev has taken a different stylistic tack. Whether through training or personality, he acts more like a western correspondent than any of his predecessors.

Instead of gunny-sack-cut heavy worsted wools, Shalnev looks like he's visited Brooks Brothers or J. Press. He talks in the same ironic key as any other veteran journalist. His English is filled with an admixture of British and American idioms. When a Sam Donaldson takes a verbal slash at him, Shalnev smiles and slashes back.

"They think I'm a comedian?" Shalnev says. "Oh, c'mon. It's not true."

Although he was transferred from the New York bureau of Tass to the White House assignment more than a year before Mikhail Gorbachev assumed leadership, Shalnev can, in certain superficial ways, be considered a part of the new Russian interest in image and press relations.

Shalnev is a "100 percent native Muscovite," the son of a foreign ministry official. After graduating in 1969 from Moscow University's faculty of Oriental languages, where he learned Hindi and Urdu, he spent four years for Tass in New Dehli, two years at the home office in Moscow, four years in the London bureau and another year in Moscow before joining Tass' eight-person bureau in Washington. He is the author of a book on Britain, "Between the Lines of the Unwritten Constitution," and one on the United States, "Nine Events in One Year."

Western correspondents seem more comfortable with Shalnev than they did with "Boris."

"He makes an effort to be one of the boys," says Donaldson. "I called him 'the Colonel' like the guy before him, but Alexander said, 'No, no, I'm just the Major.' And when I asked him when we'd throw him a defection party, he actually smiled."

Even Speakes has taken his pokes at Shalnev. After rendering one of the president's particularly harsh anti-Soviet stances, Speakes looked up, smiled at Shalnev and said, "Take that!"

"I don't know much about this semimythical 'Boris,' " says Shalnev. "My style is just my style. I've always thought that this approach would be best, instead of just browsing through all the papers and watching the television reports. You have to get along with people."

Shalnev says he does not exactly find all the kidding at his expense hilarious, but "I accept it as the usual thing. I'm accustomed to it, though sometimes I wonder."

Tass may seem roughly analogous to, say, the Associated Press, but the resemblances are slight. And to say that Shalnev is a "western-style" reporter because he makes an occasional joke would be like mistaking Yuri Andropov for a "western-type leader" because he may have listened to Benny Goodman.

Like every other Soviet press organization, Tass is an arm of the state, and Shalnev is first and foremost a government employe.

When he asks questions at White House briefings they are almost always about U.S.-Soviet affairs. Sometimes he does more than ask questions. At yesterday's press conference announcing the return from the West to the Soviet Union of Vitaly Yurchenko, a top KGB official, Shalnev's question included a diatribe against the "monstrous" way Yurchenko had been treated by the country that "talks loudest about upholding human rights."

Once Shalnev and Speakes got into a brief argument over an exchange between the late Soviet leader Konstantin Chernenko and the president. Shalnev demanded of Speakes a "yes-or-no answer" as to whether the president rejected certain statements made by Chernenko in an interview.

With his face reddening, Speakes said, "I would leave that to the judgment of you and the Soviets, which are one and the same in your case."

Though Shalnev is only partly a reporter in the western sense, he says, nevertheless, that "My role, as I see it, is to get as much information as I can from the White House . . . I can't afford to miss a word on Soviet-American relations and arms control especially.

"It's hard to say how we're similar or different from American correspondents, but we're covering the same news and we try not to be scooped by the other wire services."

Andrew Nagorski, a former Newsweek correspondent in Moscow who was thrown out of the Soviet Union for engaging in "impermissible methods of journalistic activities," says, "It would be ridiculous to think that the guy who was dour and built like a refrigerator was really very different from the newer, more sophisticated version. They all work for the same employer -- the Soviet government -- and they all work on a number of levels."

Beat reporters for Tass cover the State Department, Capitol Hill, the Pentagon and the White House. There is also a bureau in New York.

Tass headquarters is located in a modern building on Moscow's Boulevard Ring Road. Supplying Pravda and Izvestia and other Soviet papers with news from abroad is but a small part of the agency's function.

Using a FAX machine, telex or computer terminal, Tass foreign reporters file huge amounts of raw, "unprocessed" data: texts of speeches, press conferences, reports and western news copy.

Their problem is not so much getting information as dealing with the pile of material that mounts up every day. "I have the same access to press conferences and the releases as the American correspondents," says Shalnev. "I don't expect to be briefed in secret in some room in the West Wing, but I'm not complaining."

In Moscow this mass of information is turned into a daily booklet called White Tass. The public does not see White Tass, but it is distributed widely among bureaucrats as well as high government officials. White Tass, however, contains little or no anti-Soviet information. Red Tass (printed on red paper) contains a greater number of "unwelcome facts" that may reflect critically upon the Soviets. This is available only to a higher realm of editors, bureaucrats and party members.

Finally, only a select few are permitted to see Green Tass, which contains relatively unadulterated reports from around the world, including anti-Soviet analyses printed in the western press.

Sometimes correspondents write their own stories, but often the dispatches from Tass that appear in the pages of Pravda or Izvestia are culled from the raw material filed from abroad and written in Moscow. Pravda and Izvestia also have their own correspondents in Washington and New York.

Western correspondents in Moscow depend heavily on the Tass wire, not only to hear about news within the Soviet Union but also to get a sense of the Soviet interpretation of news from abroad.

Tass also acts as a strident mouthpiece of the government against "anti-Soviet" subjects. The agency once described the late Henry Jackson as "the henchman of reactionary circles of the military-industrial complex, the right-wing leadership of the AFL-CIO and of Zionist organizations." Objectivity is not a top priority. Reports will often begin with something on the order of "The White House has issued yet another falsification."

"You get a lot of throat clearing in the first paragraphs," says Dusko Doder, a former Moscow bureau chief for The Washington Post. "You usually get the news somewhere near the bottom. You have to learn how to read it."

The Washington field office of the FBI as well as counterintelligence arms of the CIA and the Defense Department monitor the activities of Soviets working in Washington, including journalists. Says one FBI source, "Journalists have a certain access and freedom of movement that other Russians may not, so we always assume there are intelligence officers in that context."

David Satter, who was Moscow correspondent for Britain's Financial Times for six years and is now writing about information in Soviet society, says, "The KGB has access to everything and anyone. There's no separation saying this one's only a journalist or a diplomat."

In 1956 Lt. Col. Ismail Ege, who fled to the West after 17 years in the Soviet Army, told the Senate internal security subcommittee that 80 percent of the personnel of Tass "are Soviet spies." And that image has persisted. But one CIA source said that while a Tass reporter is likely to keep in contact with the KGB, he is not likely to be carrying top-secret information or engaging in high-level espionage. "The Russians tend to use their 'illegals,' or low-profile people, for that sort of work, not journalists," the source said.

A number of Soviet press representatives have been expelled or arrested for intelligence activities, but Shalnev dismisses the spying issue as "nonsense":

"Do you want a scoop? All that stuff, it's not correct. It's a funny question. You should be more mature. But what can I expect?"

Shalnev drives a company Chevy every morning from his apartment in Alexandria to his office at the National Press Building on 14th Street NW. He lives here with his wife Yelena, but his daughter lives in Moscow. "She's 17, too old for the Russian school here, so she went back," says Shalnev.

"Life is terrible here; almost all the time you are working," he says. "It's the life style of Washington, D.C. It may be the craziest city I've ever been to. Sometimes you think to yourself, 'Good grief, you've got to do something other than work.' But it's rare."

Shalnev's work habits are legend among White House officials. Karna Small, an assistant to National Security Adviser Robert McFarlane, says, "Invariably, whenever Bud McFarlane gives a speech, the first call the next morning is a request for the transcript from Alexander."

Shalnev says he relaxes "once in a while" with a book, an occasional movie or shows on public television. He gets a kick out of Neil Simon.

But the Soviet Union has not sent Shalnev to Washington to visit the theater. Last week, when senior journalists from Pravda, Tass, Izvestia and Novosti arrived in Washington to meet with the president, Shalnev was busy escorting his seniors around town.

Shalnev relayed the president's desire to meet with the Soviet press to officials in Moscow this summer, and then acted as intermediary in the ensuing negotiations. During the Reagan interview Shalnev did not ask questions, but rather stood off to the side as an observer in deference to his seniors.

The White House assignment is one of the top jobs in the foreign press corps, and the predictable path would be for Shalnev to return to the home office. "I don't know exactly what I'll do," he says. "If I had to guess, I'll probably stay in Washington for a year or two and then go back to Moscow."