WASHINGTON (AP) _ Under Lenin's dour gaze from a giant portrait, Soviet officials uncorked their new export supervodka and hustled American guests like born-again capitalists, with grins, backslaps and heaping bowls of caviar.

Glasnost was in full flower Wednesday night at the Soviet Embassy, and warm feelings of ''openness'' were stoked by frequent gulps of Stolichnaya Cristall, the ultra-premium Russian vodka that will appear on liquor store shelves in 10 American cities this week.

''You might ask, what is the difference between Stolichnaya and Stolichnaya Cristall,'' Soviet ambassador Yuri V. Dubinin smilingly told the happy throng. ''I suspect the effect is just the same, but Stolichnaya Cristall is better for your health.''

If Dubinin and his marketing comrades get their way, Stolichnaya Cristall will be good for the health of the Soviet economy, which suffers from a shortage of hard Western currencies.

The Commerce Department says United States imported a record $1.7 billion in Soviet goods last year, compared with U.S. exports of nearly $2.8 billion to the Soviet Union. The U.S. export figure, representing largely grain, was up 87 percent from the previous year but below the record $3.6 billion in 1979 before the Soviet invasion of Afghanistan prompted a U.S. embargo.

Stolichnaya Cristall, like the older Stolichnaya brand, is bought by PepsiCo Inc. for resale in the United States under a 1972 agreement that allows the Soviets to produce Pepsi Cola at 21 bottling plants. Under a newly negotiated deal, 26 additional Pepsi Cola plants will be opened within the next few years.

''It's an old-fashioned barter deal,'' said PepsiCo chairman Donald M. Kendall, who received the first bottle of Stolichnaya Cristall from Dubinin at the embassy reception.

Stolichnaya Cristall is named for the Cristall distillery in Moscow, one of the two plants that produces the prestige export vodka. The latest version, developed in 1982, is made from the finest winter wheat and the purest spring waters from the Moscow region, said Suren S. Santurian, senior engineer of Amtorg Trading Corp., the Soviet government's export marketing agency.

Drawn from the finest 5 percent of the alcohol that trickles through three sets of activated charcoal filters, Stolichnaya Cristall is ''like taking the cream off the top of the milk,'' Kendall said.

Retail U.S. prices will be ultra-premium as well. A bottle of Stolichnaya Cristall will sell for $18 to $20 retail. That will be about $5 more than regular Stolichnaya, which is billed as ''the only authentic Russian vodka available in the United States.''

The new vodka, served in brimming shot glasses from silver trays by waiters in black ties, was a hit among the several hundred American representatives of the wine and spirits trade, members of Congress and journalists who attended the reception.

The guests also feasted on iced bowls of Petrossian caviar, Norwegian smoked salmon, grilled beef filets and chicken breasts, lime bavarian cream charlotte and black Russian tea.

One reporter observed after downing a shot glass of Cristall: ''It's real smooth, compared to the cheap rotgut I buy. It's like a sipping whiskey. There's no burn. It just goes straight down.''

Stolichnaya is extremely difficult to obtain in the Soviet Union, where it is reserved for export, foreigners and the Soviet elite - who have access to special consumer goods stores in Moscow.

PepsiCo officials said only a few thousand cases will be available in the United States this year for stores in Atlanta, Boston, Chicago, Dallas, Houston, Los Angeles, Miami, New York, San Francisco and Washington.