Beck, SPD chief and premier of the state of Rhineland-Palatinate, wrote in The International Herald Tribune on Tuesday that the missile shield should be discussed further within NATO and the NATO-Russia Council in a reassessment of whether there is actually a need for the defense system.

"That means not only informing the members of these organizations about one's own plans but also entertaining a willingness to abandon them if necessary," he wrote.

Beck pointed out that the plans to station the defense system in Poland and the Czech Republic had inflicted "great harm" on relations between Russia and the United States and Europe.

He also called for a new round of global disarmament: "Disarmament policy must ... be urgently re-established as a key regulatory principle in international relations," he wrote. "Major international disarmament regimes are already in shreds or have been completely destroyed."

Money better spent elsewhere?

Beck stressed the importance of close ties between the US and Germany, but also used the opportunity to point out that Washington had already sunk more than $100 billion in developing the shield, which may not even work. That money could have been spent differently and "achieved more for the security of the United States," he added.

As head of the SPD, which is part of Christian Democrat Angela Merkel's government coalition, Beck is the party's most likely candidate for chancellor in 2009. In the past, he has been openly critical of US plans for the defense system meant to block attacks from hostile countries, warning in March that it could spark a new arms race. Those comments led to tensions within Germany's governing coalition as his column on Tuesday was also likely to do.

Chancellor Merkel has been muted about the defense shield plans, only saying there should be a debate on the missile shield within NATO and that the EU should "present a common front" on it.