German Chancellor Angela Merkel's partners in government criticised US plans to put a missile shield in central Europe, saying the project could spark a new arms race.
German Foreign Minister Frank-Walter Steinmeier, a member of the centre-Left Social Democrats (SPD), warned Washington in a contribution to the Frankfurter Allgemeine Sonntagszeitung not to try to split Europe into "old" and "new" with its plans.
Kurt Beck, the SPD chairman, went further, urging Europe to unite against a project Russia sees as an encroachment on its former sphere of influence and an attempt to shift the post-Cold War balance of power.
Under the plan, the US wants to deploy a radar system in the Czech Republic and 10 interceptor missiles in Poland by 2011-12. It says the system is designed to counter threats from so-called "rogue states" such as Iran and North Korea.
"We don't need new missiles in Europe," Mr Beck told the Bild newspaper, in an echo of the fierce debate in Germany during the late 1970s over the deployment of US Pershing medium-range nuclear missiles in Europe.
"The SPD does not want a new arms race between the USA and Russia on European soil. Europe must speak with one voice on this," he added.