THE failed coup attempt against Soviet President Mikhail Gorbachev presents opportunities as well as challenges for United States policy toward the Soviet Union.In the short term, administration officials - including President Bush - and Soviet specialists see a boost to relations. With the removal of the top conservatives in Gorbachev's leadership, his hand has been freed to take a more radical approach on reform. "The fears that some of us have had - many of us, actually - about right-wing take-overs will no longer be as extant," Mr. Bush told reporters Wednes-day. "I expect the relationship to be, if anything, even better." A key question is how Gorbachev will handle the new lease on his political life. Before his detention, his popularity had plummeted to less than 10 percent in opinion polls. But if he follows the cue given him by the Soviet people - that they back reformist, democratically elected rulers like Russian Republic President Boris Yeltsin - he could build back a mandate. "It's immensely easier now" for Gorbachev to supply the missing national program, says Tyrus W. Cobb, a Soviet specialist at the Center for Strategic and International Studies in Washington. "There could not have been a better script to remove Gorbachev from his precipice." Some analysts also suggest Gorbachev may decide he needs to hold direct popular elections, perhaps as early as this fall, for the presidency of the Soviet Union. "If anything," says a senior administration official, "the coup attempt has shown the value of being elected now in the USSR." If Gorbachev does manage to turn the coup to his political advantage, then the US's main interlocutor would be operating with more authority than he would have possessed otherwise, at least in the near term, says Peter Reddaway, a professor of political science at George Washington University. The leadership crisis also makes it possible for Yeltsin to extend his tactical alliance with Gorbachev, which was waning before the coup and which US policymakers believe is central to any forward movement on the key issues of economic and political reform. "Gorbachev will have to commit himself more strongly than before to the reformists and that will make it easier for the West to help," says Dr. Reddaway. "In the short term, the situation will be improved all around." Gabriel Schoenfeld, also of the Center for Strategic and International Studies, predicts the West will be willing to take more of a gamble in giving the Soviets tangible aid, now that there is less worry over hard-liners undoing reform. "The West has seen what's at stake if reform isn't successful," says Mr. Schoenfeld. "The coup has paved the way for economic reform. The people will have to make sacrifices, but now they, too, realize where the alternative lies." The senior administration official, speaking on background, suggests that, in the wake of the coup, there will be a desire in the West to make a gesture of support for the Soviet people. One way to do that, he says, would be to give the country a modicum of humanitarian aid as a taste of the larger-scale aid that may follow if the Moscow does take the plunge into radical market reforms. Over the long term, the coup could complicate US policymaking. Undoing the coup will do nothing to retrieve the Soviet Union from economic chaos. Moreover, with the power of the center substantially weakened, political stability could be taxed as never before. "More will depend on local factors," says Reddaway. "Every republic is different, and those differences are going to be far more important now than ever in the past. Every question you would ask about the Soviet Union before the coup you now have to ask 15 times." The new union treaty will play a key role in how the US is able to relate to the different power centers in the republics. It devolves considerable decisionmaking power to the 15 republics - for example, granting them control over their economic resources. But many provisions of the treaty, which is expected to be signed eventually by nine or 10 of the republics, are vague, and the US will not be able to work within its new structures until it sees how it is implemented. For now, the Bush administration plans to continue diversifying its contacts with democratic forces throughout the USSR, while dealing with the center on areas where it has jurisdiction, such as arms control. This dual-track framework for relations, which has been developing over time, paid dividends during the coup. Bush has met with Yeltsin several times and appeared comfortable throwing his full support behind him during the crisis. Yeltsin's new elite status shakes the old order of US-Soviet relations, in which the US openly backed Gorbachev. If tensions flare up again between Yeltsin and Gorbachev after a while, as some analysts predict, the US could be put in an awkward position. "There's now a kingmaker who is much more powerful than the king," says William Zimmerman, director of the Center for Russian and East European Studies at the University of Michigan. "Yeltsin will seize the moment to press Gorbachev to move forward into real marketization and to give power to the republics." The US itself may want to seize the moment with Gorbachev in certain long-troublesome foreign policy areas, such as Cuba and Afghanistan. If Gorbachev has been thwarted in a desire to cut back on aid to those countries by hard liners, now could be his chance for a shift in policy.