WASHINGTON -- President Clinton, preparing for a four-nation trip to Europe, says "a responsible, strong Russia" is not a threat to Central and Eastern Europe.In a series of interviews with foreign journalists and reporters from ethnic newspapers in the United States, Clinton said he could sympathize with anxieties within Poland and elsewhere about what one questioner called "renewed pressure and imperialistic tendencies" by Russia.But he added: "I think it's important not to overreact to that. We watch this with great interest. And our concern and commitment to Poland is great."In an interview transcript, Clinton said, "There will be tensions and disagreements from time to time, but I believe we have a united Europe with a responsible, strong Russia, and we are going to work for that."Russia enrolled last month in NATO's Partnership for Peace, which holds out the possibility of eventual NATO membership. In addition, Russia and NATO adopted a joint declaration that said both have "important contributions to make to European stability and security."Russia's potential influence is a sensitive matter in other East European capitals, which worry that Moscow could have too strong a say in the alliance's dealings with them.Clinton cited Russia's efforts to help promote peace in Bosnia and Georgia and progress on withdrawing its troops from the Baltic states as examples where Russia, "while more active in its area, in its neighborhood, if you will, has been largely constructive.""I believe that we have a chance to work out a constructive relationship where the Russians say, 'We want an active foreign policy, but we will recognize the freedom and the independence of all our neighbors,'" Clinton said.Asked if he could envision potential reunification of Russia with Ukraine, Belarus or other former Soviet republics, Clinton said, "It depends upon whether such movements would develop out of a genuine democratic movement and a free will of the people involved."I think the people of Central and Eastern Europe will know in their hearts and minds whether it was a grassroots, honest, democratic impulse," he added. "And that will be the test."Asked when NATO would be ready to offer former Warsaw Pact members full membership, Clinton said that he had no doubt NATO would be expended but that some members were not yet ready for that step."I can't do that alone," he said. "That probably won't be done until sometime next year because of the feeling of all the NATO members about it."He stressed that Russia, where there is resistance to early NATO membership for Poland, would not have veto power over what countries can join, nor was it true "that something bad has to happen in Russia before we expand NATO."Clinton said that in the interim, it was important not to underestimate the Partnership for Peace, which he said demonstrates "a real desire to try to prove that we can unify Europe from a security point of view."Clinton leaves Tuesday on a week-long European trip, stopping first in Latvia to become the first U.S. president to visit a Baltic state.Next, he travels to Warsaw, Poland, to meet with President Lech Walesa and address the Polish parliament. Then he will travel to Naples, Italy, for the annual economic summit of industrialized nations and talks with Russian President Boris Yeltsin.