US Defence Secretary Donald Rumsfeld has said the new members of Nato are taking the lead in confronting new threats to security and in injecting a fresh vision to the old Atlantic alliance.
The US and Europe 'are joined together by more than common interests'
Correspondents say his remarks echo a controversial statement made by Mr Rumsfeld, in the run-up to the Iraq war, about the old and new Europe.
He was speaking in Germany - a strong opponent of the war in Iraq - a country which Mr Rumsfeld has described as part of "old Europe".
It is Mr Rumsfeld's first visit to Germany since the war in Iraq, and is part of a European tour which started as a thank-you gesture to nations that supported the US-led conflict.
Some want to define themselves by their opposition to the US - as some sort of 'counterweight' to America
Mr Rumsfeld gave a major speech at the Marshall Center for European Studies, a joint US-German project at Garmisch in Germany.
"Many nations in Europe, but not all, correctly see the nexus of terror and weapons of mass destruction as the biggest threat and recognise that transatlantic unity is more critical than ever if we are to successfully deal with that threat," he said.
"Some want to define themselves by their opposition to the United States - as some sort of 'counterweight' to America.
"Most reject the argument that they must choose between Europe and America and recognise that a robust transatlantic relationship is not only compatible with European integration, but critical to our mutual security," he said.
BBC Pentagon correspondent Nick Childs says that despite Mr Rumsfeld 's remarks, he tried to play down some of the differences with older Nato allies that arose over the Iraq war.
There may be arguments from time to time, said Mr Rumsfeld, but Americans and Europeans were joined together by more than common interests.
Mr Rumsfeld's visit comes at a time when the US is considering major changes in its military deployments around the world, including moving away from traditional bases in countries like Germany.
US moves to secure immunity for its personnel have caused tensions
His visit also comes amid fresh transatlantic tensions over Washington's moves to gain another year's exemption from prosecution from the International Criminal Court, a war crimes tribunal set up last year.
The US has accused several EU countries of undermining its efforts to arrange such agreements by lobbying countries not to sign.
A note issued by the US to embassies and obtained by the Washington Post warns that opposition to the US efforts to gain immunity will harm transatlantic ties.
Germany was one of the countries which received such a warning, BBC News Online has learned.
Mr Rumsfeld is in Germany along with 10 European defence leaders to mark the
10th anniversary of the George C Marshall Center for Security Studies, which trains military and civilian officials for leadership roles in their defence establishments.
After Germany, the US defence secretary will head to Brussels for a Nato meeting on reforms to the alliance's command structure and forces, as well as efforts to create a peacekeeping force in Iraq.
Mr Rumsfeld has already visited Portugal and Albania to thank them for their support in the war.