FOR many Europeans, Bill Clinton represents the next generation of leadership in the West, full of energy and domestic activism, compared with his older and more politically troubled NATO colleagues.
But as he begins his first major-league diplomatic mission, President Clinton has made his European colleagues edgy about the strength of his commitment to Europe.
Over the course of two days here, NATO and European Union leaders mostly will discuss how to begin integrating the former Soviet bloc countries into the alliance. But the heart of Clinton's mission in Brussels is to assure somewhat dubious Europeans that the United States is still the defender of Atlantic security.
Rarely has a postwar US president waited so long to visit Europe and symbolically reaffirm US interest. And this at a time when American troop presence in Europe is moving from over 300,000 when George Bush took office, to 150,000 when he left, to 100,000 under Clinton.
President Bush had been abroad in his first six months as often as Clinton in his first year. But then, Clinton takes as absorbed an interest in domestic policy as Bush did in diplomacy. This has not been lost on the Europeans, who rely on the US for military security and geopolitical stability - concerns that have not turned out to be obsolete in the post-cold- war world.
When the allies see an American administration preoccupied with domestic concerns and ``unprecedentedly weak in foreign policy, it's very unnerving to them,'' says Peter Rodman, a former staff member of the White House National Security Council. ``What they need to hear from him is a firm commitment to America in Europe in the security area.''
``It's going to be a real test of his leadership,'' says Robert Lieber, a professor at Georgetown University.
The Clinton administration achieved one significant success for world security before the president even left the US. After negotiating in Washington for most of last week, American and Ukrainian officials all but closed a deal on Saturday for Ukraine to dismantle its nuclear warheads in return for $12 billion in aid.
Many American leaders and experts did not expect Ukraine to give up these weapons, especially since the December elections in Russia showed a strong minority sentiment in favor of a return to empire.
Clinton faces this week's test of leadership at a time of unusual personal difficulty. He arrived in Brussels yesterday from his mother's funeral in Hot Springs, Ark.
The aura of something to hide surrounding his personal investment in the now-defunct Whitewater Development Company grew by the day last week with White House misstatements and clumsy handling of the issue. The issue competed with NATO's future for press attention and will greet the president on his return.
While he is here, Clinton clearly intends to convey a solid commitment to Europe. This is only the first of three trips he plans to make here through the spring - a positively Bush-like level of diplomatic activity.
But Clinton has not arrived in Europe with a strong record in foreign policy. The Haiti policy he campaigned on - as one of his few sharp differences with Bush in foreign affairs - did not even survive his transition before he reverted to the Bush viewpoint.
His tough talk on the Balkans - threatening airstrikes against the Serbs for shelling Sarajevo - has neither slowed Serbian shelling nor brought airstrikes.
Secretary of State Warren Christopher caused some dismay last spring when he made the rounds of Western European capitals to discuss Balkans policy. The mission was presumably to promote and refine the American proposal to lift the arms embargo on Bosnian Muslims and use air- strikes against their attackers.
But Mr. Christopher seemed to listen to European ideas passively, an unnerving experience in an alliance that has been built around American leadership.
THE summit here this week is Clinton's chance to begin reasserting that American leadership. Clinton intends to shift the focus of American foreign policy from military security to trade and economics whenever he can, according to senior aides. But security remains a much more concrete issue in Europe.
Clinton's profile in Europe is somewhat traditional for a Democratic president. Europeans have often preferred Republicans in recent history because they have been more internationalist in their concerns and have had a strong strategic thrust.
Democrats, on the other hand, meaning chiefly Jimmy Carter and Bill Clinton, have taken office when American concerns have turned most sharply inward.
Dr. Lieber notes, however, that every Democratic president serving in this century has had his presidency overshadowed by a major foreign policy eruption. That historical pattern means it would serve Clinton well to attend closely and ably to the front-rank world concerns on this trip while the going is relatively smooth.