The United Nations is marking its 60th anniversary at a time of strained relations with its host country and largest financial backer, the United States. But both sides continue to see the relationship as important and necessary.

Ties between the United Nations and its host country may have hit an all-time low two and a half years ago, when the United States led a coalition into Iraq without the Security Council's authorization.

Not long after, Secretary General Kofi Annan named a high-level panel to recommend changes at the United Nations, a move seen partially as an attempt to limit the ability of member states to act unilaterally.

When he unveiled his reform proposal last March, saying he wanted it approved at the 60th anniversary summit, he left no doubt that one of its aims was to limit the possibility of unilateral action such as the move to topple Saddam Hussein.

"I think that the argument that comes through the report is very clear: that we live in an interconnected world, in a world where we face many challenges, many threats -- threats that no one country, however powerful, can face alone -- and that we need to work together to contain these threats? So I think the collective effort of all of us working together is in the national interest of individual member states. I think that an effective and functioning United Nations is in the interests of the United States and its people, as it is in the interest of other nations and their peoples," he said.

When he was asked in a subsequent British Broadcasting Corporation interview whether he considered the invasion of Iraq illegal, Mr. Annan said yes.

Such words did not go down well with the Bush administration and many in Congress who see the Iraq campaign as both legal and proper.

Congress quickly appointed its own panel on U.N. reform headed by former House Speaker Newt Gingrich and former Senate Majority Leader George Mitchell. Several congressional committees launched investigations into allegations of corruption in the U.N.-administered Iraq oil-for-food program. And President Bush named outspoken U.N. critic John Bolton to be his ambassador to the world body.

Many veteran U.N. observers say such tensions are probably unavoidable. Professor Edward Luck of Columbia University says that while the invasion of Iraq may have marked a low point in U.S.-U.N. relations, a certain amount of friction is to be expected, given what he calls the "asymmetries of power" between the United States and other U.N. member states. "On the whole, the U.S. relationship is more troubled with the U.N. on balance than at most times in history. The U.S. has always had considerable ambivalence about the U.N. Partly because?. for a very large power, fitting into an organization of 191 countries is a bit awkward," he said.

Awkward it may be, but friends and adversaries alike agree that in the end, both the United States and the United Nations need each other.

Jan Eliasson takes over this month as president of the General Assembly after five years as Sweden's ambassador to Washington. He makes the point that the United Nations serves a vital purpose in the exercise of U.S. leadership. "There's no denying that the United States is the leading superpower today, and it's been recognized all over. I would hope that the superpower would also realize that good multilateralism is in its interest. I think the experience of Iraq as compared to Afghanistan could speak its own language. And I would hope that the United States would be in line with its traditions, a partner in international efforts," he said.

Former Senator George Mitchell says his congressionally funded study of the United Nations reached essentially the same conclusion. He sees no contradiction between U.S. interests and those of the United Nations. "It is not a conflict. The fundamental aspirations of people everywhere are similar?.there may be limited tactical disagreements about how to proceed in the short term, but the values and aspirations Americans have are the same as people elsewhere," he said.

Such disagreements as the one over Iraq have led to recent criticism of the world body in some sections of U.S. public opinion. But Columbia University's Edward Luck says despite its flaws, the United Nations enjoys strong support from the vast majority of Americans. "The most recent Gallup Poll showed only 13-percent of people want us to leave the U.N.?.but at the end of the day, the public feels we ought to pay our dues, stay in the U.N., ought to be a good international citizen, but at the same time if our national interests are such that we have to vote alone, we're not embarrassed to do so. We have a lot of confidence in our basic principles and purposes as a nation, so I think it will continue to be an awkward relationship, but neither side can afford to give up on the other," he said.

Professor Luck says Washington's willingness to "go it alone" on matters of principle, and what he describes as the "asymmetries of power" mean ties with the United Nations will remain "very delicate".

Nevertheless, a broad cross-section of analysts and diplomats agree that, despite 60-years of pressures, the foundation of the relationship is perhaps stronger than ever.