MOSCOW, SEPT. 21 -- Once regarded as the infallible voice of the Soviet Communist Party, Pravda today took the unprecedented step of apologizing to Kremlin radical Boris Yeltsin for a slashing attack on his behavior while in the United States. Pravda's publication of an account of Yeltsin going on a drinking and shopping spree while in the United States has caused an uproar here. The editorial offices of major Soviet newspapers have been besieged by angry callers defending the former Moscow Communist Party chief. A commentary in the progressive weekly Moscow News said Pravda's decision to reprint a story about Yeltsin that first appeared in the Italian newspaper La Repubblica violated the rules of fair journalism. It accused the Communist Party organ of making no effort to check the facts contained in the original article. "It seems the entire Soviet press corps in the United States was on vacation," wrote Vitaly Tretyakov, deputy editor of Moscow News, noting that the Soviet newspaper devoted little coverage to Yeltsin's eight-day tour of the United States. Pravda -- the word means truth in Russian -- today said its correspondent in Washington had spoken to the author of the La Repubblica article, Vittorio Zucconi. It quoted him as saying that he had relied on secondary sources, including a Sept. 13 article in the Style section of The Washington Post, for his story. However, his story went well beyond the details reported in The Post, maintaining, for example that Yeltsin had planted a drunken kiss on a senior official of Johns Hopkins University at 6:30 one morning. "Let's drink for freedom," Zucconi reported Yeltsin as saying, without revealing the source of the alleged quote. {On Wednesday, Zucconi told a Knight-Ridder reporter that his story contained several inaccuracies, including quotes from an Esalen Soviet American Exchange Program official who did not exist and details about Yeltsin's behavior at a party that Yeltsin never attended.} "The editors of Pravda apologize to Boris Nikolaevich Yeltsin. We suggest that the correspondent and editorial board of La Repubblica do the same," said a two-paragraph item on the bottom of Page 7. The La Repubblica article had seemed potentially damaging to Yeltsin, as ordinary Soviets are much more inclined to believe the foreign press than their own official media. But the lack of substantiation for the claims by Zucconi and Pravda's remarkable apology are now likely to work to Yeltsin's political advantage. Ousted from the Politburo in 1987, Yeltsin has succeeded in creating an image for himself as a populist politician battling conservative bureaucrats and party privilege. His popularity has been fueled by clumsy attacks on him in the official press. Pravda has generally been loath to print corrections of factual errors, let alone apologies to public figures. Although it now competes for readers with several more progressive newspapers, its editorials and articles are still required reading for hundreds of thousands of party officials around the country. The decision to publish an apology to Yeltsin could undermine the position of Pravda's veteran editor, Viktor Afanasyev, who is widely regarded as a leading conservative spokesman. The 66-year-old chief editor has already survived several attempts to replace him with a journalist more clearly committed to the reformist policies of Soviet leader Mikhail Gorbachev. In his article, Zucconi depicted Yeltsin as a hypocritical drunk who squandered enormous lecture fees on video players, suits and shoes. Zucconi picked up details of Yeltsin's heavy drinking from The Washington Post, which attributed to a high official at Johns Hopkins University the statement that Yeltsin had drunk 1 1/2 quarts of Jack Daniel's whiskey during the night he spent at the school. This week, following the extreme reaction in Moscow to the story, Hopkins President Steven Muller amended his account. Last week he told reporters that Yeltsin had drunk that much whiskey, but this week he said he assumed Yeltsin had shared the bottles with others in his group. Since Yeltsin returned from the United States on Monday, he has attended various rallies of enthusiastic supporters around Moscow at which he has denounced the Pravda attack as "slanderous."