THE world has caught up with Bill Clinton. If you ever believed that as president he could keep his attention on domestic affairs, that illusion is gone. Russia, Somalia, Haiti, Bosnia: The list of foreign crises is growing, and they will not go away. For two reasons foreign policy is a difficult area for this president. One lies in himself, the other in the nature of international problems today. "Somehow," the Economist wrote two weeks ago, "the fire is not in Mr. Clinton's belly when he speaks on foreign policy." Anyone who heard him on health care and on Somalia will understand. On health he was sure on his facts, confident, enthusiastic. On Somalia he seemed tentative, fuzzy, unconvincing. Of course Somalia is a complicated problem. But so is the issue of national health care; there Mr. Clinton may not have the perfect solution, but he is so informed and committed that he communicates his conviction. In our democracy, foreign policy must have public support to be successful. And the nature of the problems in the world makes it much harder to get that support now than in recent decades. For 40 years after World War II most Americans saw communism as a menacing danger to our security and freedom, and they supported programs to oppose it. The Truman Doctrine, the Marshall Plan, the North Atlantic Treaty, Korea, Berlin, even far-fetched Grenada: Presidents could rally public support in the Manichaean framework of the Cold War. Now there is no great enemy. Instead there are brutal internal conflicts and humanitarian crises. To rally Americans for intervention in those matters is difficult. Indeed fewer and fewer Americans have any interest in foreign affairs. President Bush, goaded by Prime Minister Margaret Thatcher, managed to rouse support for war on Iraq. He exaggerated: Saddam Hussein was "worse than Hitler." But the Iraqi invasion of Kuwait was undisguised aggression, and the threat to Western oil supplies did present a risk to national security. To intervene effectively in any conflict abroad a president must persuade the public that the United States has a national security interest there. Mr. Clinton did so in the Russian crisis and did it well. From the first, clearly and consistently, he called for support of President Yeltsin as the best hope of building democracy and preventing a renewed threat to our interests from Moscow. Somalia is the opposite case. It presents no threat to American security. I favored the dispatch of American forces last year to prevent mass starvation, not foreseeing the larger political difficulties that have arisen. But Mr. Clinton's policy to deal with them, sending more troops while swearing to pull them all out by March, is muddled and unconvincing. What good are we doing? What is our interest? Americans do not know and hence do not support the policy. But Mr. Clinton's worst failure in foreign policy has been in Bosnia. The humanitarian interest is obvious when hundreds of thousands of people have been raped, murdered and driven from their homes because of their religion. But there is also a powerful security interest. The greatest challenge that has emerged in the post-Cold-War world is ethnic conflict. Freed from the constraints of the superpower rivalry, ethnic groups in the Balkans and the former Soviet republics have turned on each other with terrifying savagery. What is happening threatens to destroy the European stability that is so essential to America. Bosnia was the place to draw the line. It was the victim, like Kuwait, of open aggression. Serbian ethnic cleansing was more Hitlerian than anything Saddam Hussein did. Sen. Bob Dole was right when he told Mr. Clinton last summer that in terms of our national security interest we should get out of Somalia and get into Bosnia. Mr. Clinton could have stopped the aggression against Bosnia if he had acted forcefully soon after taking office, making clear to Slobodan Milosevic that we would bomb Serbian forces if they continued their sieges and massacres. Instead he deferred to appeasers in Britain and France. A president who wants to focus on domestic affairs must put foreign policy in a framework that Americans understand and that makes them feel secure. Mr. Clinton still has that job ahead of him. Anthony Lewis is a columnist for the New York Times.