WASHINGTON — UNTIL four years ago, Soviet authorities did everything they could to keep their citizens from listening to Radio Liberty, the United States-financed shortwave service broadcasting to the Soviet Union.Now, following its key role as an up-to-the-minute purveyor of information during last month's coup attempt, Radio Liberty (RL) is no longer merely tolerated - Russian President Boris Yeltsin welcomes it. In a surprise decree last week, President Yeltsin invited the radio to open a permanent bureau in Moscow and offices elsewhere in the Russian Republic. Yeltsin's stipulation that the radio be provided "with the necessary channels of communication" has sparked hopes that the Russians may permit RL to broadcast on medium wave - or the AM band - which would allow citizens with ordinary radios to tune in. "Radio Liberty will now be more timely and more accessible," says Mark Pomar, executive director of the Board of International Broadcasting, the US agency that oversees RL and its sister service, Radio Free Europe (RFE), which broadcasts to Eastern Europe and the Baltic republics. "It will be seen as the domestic radio station that it is. [Yeltsin's decree] legitimizes our presence in the Russian Republic." Radio Liberty and Radio Free Europe appear to be undergoing a metamorphosis from a surrogate provider of domestic news to countries with heavily censored media, to a teacher for Eastern Europe and the Soviet Union's fledgling independent news media. With democracy breaking out all over Eastern Europe, some US policymakers looking for budget cuts have argued the $200 million service can be scaled back and, in some countries, phased out. But leaders in Poland, Czechoslovakia, and Hungary have written letters to President Bush, Secretary of State James Baker III, and Radio Free Europe-Radio Liberty director Eugene Pell, imploring them to keep the service going. Radio officials agree that eventually the services will no longer be needed but argue that these countries are not yet ready to be weaned. The new independent media still do not have the credibility of Western news outlets, multiple international wire services and modern broadcast facilities, or experience in Western-style newsgathering. "In many countries, the structure is there, but they don't have the raw talent yet," says Gary Thatcher, deputy director of Radio Free Europe. He says RFE-RL has received 10 times as many applicants as it can handle for a training program for 12 East European and Soviet journalists. In the 12 non-Baltic Soviet republics, RL already has a stable of 50 to 75 regular free-lance reporters. In the Baltics, RFE relies on 15 to 20 reporters. During the coup, RL had two reporters inside the Russian parliament building and RFE's Polish service had one, in addition to numerous other journalists phoning in reports and interviews from around Moscow and the rest of the country. Under Yeltsin's decree, the Russian Republic's Ministry of Foreign Affairs will now grant official accreditation to RFE-RL correspondents. Yeltsin also directed the mayor of Moscow to assign RFE-RL office space.