MUNICH, Germany (Reuters) - The European Union and the United States on Saturday aired mutual suspicions about each other's main security projects and the potential threats they might pose to the survival of the Atlantic alliance.

In a sustained marathon of polite criticism at a Munich security conference, the United States made clear its controversial national missile defense (NMD) would go ahead, and the EU affirmed its rapid reaction corp would soon be an operational reality.

Each side forcefully assured the other that collective security and NATO solidarity would benefit, not suffer, as a result of the project.

Each was met with undiminished skepticism, foreshadowing a testing year for NATO as their plans advance.

Ministers anxious to avoid a public clash as President George Bush takes the helm in Washington stressed that patience and dialogue could overcome any temporary differences.

Senators, members of parliament, ambassadors and security analysts spoke more freely, and seemed less sure.

Plain-Spoken Mccain

``The strains affecting the North Atlantic alliance are considerable. The issues that confront us go to the very core of our existence as an alliance,'' said U.S. Senator John McCain.

``Fundamental questions regarding the future of NATO stand before us,'' the Republican told the annual Munich conference. ``I am afraid...that our geographical divide is increasingly becoming a functional one. Our perspectives are diverging.''

McCain said America would do whatever it had to do to counter adversaries possessing weapons of mass destruction.

The German Christian Democratic Party's Karl Lamers, in a frank exchange with the forthright senator, said many Europeans saw NMD as an American ``dream of invulnerability, which we know is futile,'' but which would wreck key arms treaties.

McCain said the European Union's planned autonomous force for crisis management had sown doubts, raised tensions and created ''unneeded acrimony'' in the alliance.

French Defense Minister Alain Richard rejected that.

The EU Corps ``is not and never will be an alternative to NATO,'' he said.

Smoother Talkers

Secretary of Defense Donald Rumsfeld again confirmed that the United States ``intends to develop and deploy'' a missile defense against a limited ballistic missile attack.

But Washington ``has no interest in deploying defenses that would separate us from our friends and allies,'' Rumsfeld said, adding: ``We will consult with you.''

It was clear, however, that consultation did not mean giving Europe a veto, although it could take up a share in the system.

Participants questioned whether Europeans would slash their health, education and welfare budgets to pay for a multi-billion dollar shield against vague threats, in addition to spending billions more on conventional arms improvements, at America's behest.

To go ahead with NMD, the U.S. must get Moscow to change the 1972 Anti-Ballistic Missile Treaty, or abrogate it unilaterally.

German Foreign Minister Joschka Fischer said Europe feared such a decision would trigger a new round of arms proliferation.

``New arms races must be avoided and further disarmament steps introduced,'' Fischer said. ``The tight net of treaties of nuclear disarmament and non-proliferation must be retained, strengthened and built up,'' endorsing Moscow's arguments.

Rumsfeld, shaking his head in disagreement, said the term ''arms race'' was an irrelevant ``leftover'' from the Cold War.

The U.S. wanted a shield ``able to deal with handfuls of things,'' not to neutralize the strategic arsenals of Russia or China, or build what conference speaker Henry Kissinger termed a ''precursor to an American first strike'' capability.

EU security chief Javier Solana said America's suspicions about the EU reaction force dividing NATO were misplaced.

``This must be in U.S. interests. After all, who wants a weaker partner? Who wants a weaker ally?'' he asked.

Rumsfeld again demurred, saying that while he was ``brand spanking new, I'm looking at it fresh and I'm a little worried.''

He said it might not bother the United States, but smaller NATO allies who were not EU members would lose their voice if the 11 EU members in the alliance arrived at crisis decision-making sessions in future with a pre-agreed position.

``Both sides have been very friendly,'' commented conference chairman Horst Teltschik of Germany. ``We had expected more tension. Let's hope it's not the calm before the storm.''