US President Barack Obama has told east European states he is abandoning plans for an anti-missile shield there, in a move that may ease Russian-US ties but fuel fears of resurgent Kremlin influence.
Russia said it would welcome cancellation of the programme, promoted by Mr Obama's predecessor George W. Bush and now a source of tension overshadowing US efforts to enlist Kremlin support over Afghanistan, Iran and nuclear arms control.
The shield, involving interceptor missiles in Poland and a radar complex in the Czech republic, was intended to defend against any long-range missile launches from "rogue" states such as Iran and North Korea. Russia saw it as a threat to its missile defences and its overall security.
"Today, shortly after midnight, Barack Obama telephoned me to announce that his government is backing away from the intention of building a missile defence radar on Czech territory," Czech Prime Minister Jan Fischer told reporters.
A senior Polish source close to the negotiations said Warsaw had received a similar message. The Obama administration seeks to "reset" battered ties with Russia so that the two former Cold War foes can cooperate on Iran, on fighting Taliban insurgents in Afghanistan and on reducing their vast arsenals of nuclear weapons.
Washington has won permission to move trains carrying supplies for US forces across Russia via Central Asia to Afghanistan, avoiding routes through Pakistan that had come under frequent attack from the Taliban.
Diplomats in Moscow say Russian hardliners could read the shield backdown as a sign of US weakness. Far from doing the bidding of the US, they may instead press for further gains to shore up Russian power in the former Soviet bloc.
That view was shared by John Bolton, a prominent hawk in the Bush administration.
"I think this is a near catastrophe for American relations with Eastern European countries and many in Nato," he said. "I think it was the kind of unilateral decision that the Bush administration was always criticised for and I think the clear winners are in Russia and Iran." Eastern European states, especially Poland and the Baltic states, saw the missile plan as a symbol of US commitment to the defence of the region against any encroachment by former Soviet masters 20 years after the collapse of communist rule.
Some east Europeans see Russia's brief war with Georgia last year and confrontations with Ukraine over gas supplies as symptoms of a Russian "neo-imperialism" driven by a view of eastern Europe as belonging to Moscow's sphere of influence.