IT is a sign of changing United States priorities that President Bill Clinton is making his first trip to Europe a year after starting his job. He put ahead of Europe a visit to Tokyo and a meeting with Asia-Pacific leaders in Seattle. As a result he will find a Europe which is wary in the West, antagonistic in the East and worried in the centre. America's perception of Asia as vital to its future is correct but its effect on foreign policy has meant that the NATO allies of Western Europe are uncertain and a little resentful. Lacking the top-of-the-list contact to which they have been accustomed, they have little direct knowledge of the president. What they do know of him cannot be comforting: foreign affairs is not one of his strengths. Yet the US remains a global power with world-wide responsibilities. So Mr Clinton has to reassure European leaders that the alliance is important. And it is, if only because of the deep economic and political instability to the East. One key to reassurance is forging a new and effective role for NATO. The anti-communist glue which held NATO together has dissolved but there are enough trouble spots (Somalia, North Korea and Bosnia, not to mention the former Soviet Union, come to mind) to ensure that a common US-European view and sense of purpose are essential to international stability. One role has suggested itself because pressure has come from the former Soviet satellite nations of central and Eastern Europe to admit them to the treaty organisation. The countries most important are Poland, Hungary and the Czech Republic, all trying to forge democracies and market economies from the chaos of their communist past and all nervous about Russia. Their anxiety has been increased by the success of the nationalist leader Vladimir Zhirinovsky in last month's elections. But Mr Zhirinovsky's popularity and his expansionist threats have created a counter-pressure not to admit these three countries for fear of antagonising the nationalist, anti-Western sentiment he has tapped - thus undermining the President, Boris Yeltsin. Mr Clinton has proposed a halfway house, ''partnerships for peace'', which envisages co-operation between NATO and the former satellites. If partnerships for peace are to be meaningful, they have to be very close and very active. No nation is likely to provide guarantees for the countries of central Europe so they have to help themselves build up the sense of security behind which they can develop their new economies and polities. This may arouse Russian nationalist suspicions and increase the discomfort of Mr Yeltsin who, despite his own dictatorial streak, remains the best hope for progress. But the most effective way to help him and diffuse tensions in Eastern Europe remains tosupport economic and political reform. The more democratic and prosperous Russia becomes, the less likely it is to be a threat to its neighbours.