President Vladimir Putin said Russia would go back to its Cold War stance of aiming its missiles at Europe if Washington went ahead with a plan to build a missile defence shield near Russia's borders.
In an interview released late on Sunday, Putin acknowledged that Russia's response risked reviving an arms race in Europe but said Moscow would not be responsible for the consequences because Washington had started the escalation.
Putin made the tough statement before what is likely to be a frosty Group of Eight summit in Germany on June 6 where, among other world leaders, he will come face to face with U.S. President George W. Bush.
Russia has not specifically targeted its missiles at Europe since the end of the Cold War but, asked if it might return to that if the U.S. missile shield plan went ahead, Putin said: "Of course we are returning to those times.
"It is clear that if a part of the U.S. nuclear capability turns up in Europe, and, in the opinion of our military specialists, will threaten us, then we are forced to take corresponding steps in response."
"What will those steps be? Naturally, we will have to have new targets in Europe."
Russia's combative response to the U.S. missile shield has prompted comparisons with the Cold War. Putin has directed angry rhetoric at the White House, last week calling U.S. policy "imperialist".
Russia has test-launched a new ballistic missile in a move it tied to the U.S. missile plans, and suspended its compliance with a treaty limiting the deployment of conventional forces near Russia's western borders.
Putin's warning that missiles might once again be pointed at European targets carries a clear political message but has few practical implications.
Even after the Cold War ended, Russia retained the capability to hit European and U.S. targets. Training ballistic missiles on a particular target is a fairly simple technical task that can be done in a matter of minutes.
Putin's comments came in an interview Putin gave to selected media from G8 countries on Friday. The Kremlin released a transcript of the interview on its Internet site on Sunday.
Russia's response to the U.S. missile moves would be to develop "more effective offensive systems", Putin said in the interview.
"We know that that risks restarting an arms race, for which we will not be responsible. It was not us who started altering the strategic balance."
Putin added: "Today we warn: if a new missile defence system is deployed in Europe there will be a response," he added. "We are forced to ensure our security."
Washington wants to locate elements of its planned shield -- including a radar station and interceptor missiles -- in Poland and the Czech Republic.
It says the shield is not a threat to Russia but is designed to protect against possible missile attacks from what it calls "rogue states" such as Iran and North Korea.
Putin said that was not credible. "There are no Iranian missiles with the necessary range," he said. "So it becomes obvious that this innovation is about us Russians."
Putin reiterated that a military escalation was not Russia's choice. "We are not in favor of confrontation," he said. "We are in favor of a dialogue.
"We want to be heard, we want our position to be understood," he said. "We do not rule out that our U.S. partners could review their decision (to build the missile shield)."
"But if that does not happen, we lift from ourselves any responsibility for the steps we take in response because we are not the ones who are initiating the looming arms race in Europe."