By Paul Reynolds
World affairs correspondent, BBC News website
The reported Russian decision not to deploy short-range missiles to Kaliningrad could, if confirmed, represent a significant move towards de-escalating tensions between Russia and the United States.
Moscow had said its Iskander missiles were to counter the US system
A Russian official, quoted by the Russian news agency Interfax, said that Russia was responding to "the fact that the new US administration is not rushing through plans" to deploy its missile defence system in Poland and the Czech Republic.
In November, Russian President Dmitry Medvedev announced that Iskander missiles, with a range of up to 400 km (248 miles), would be moved to the Kaliningrad enclave to counter the anti-missile system.
The US has said that the system is designed to stop missiles from Iran and other "rogue states" and would not affect Russian security.
"If confirmed, this is a pretty remarkable gesture," said Dr Paul Cornish, head of the international security programme at the Chatham House think tank in London.
"It could be very important, not only regionally, where it will make a difference in the perception of Russia, but also in broader terms of US-Russian relations. It looks like a major concession and, if so, is a pretty major development and quite a big step."
The Russians appear to have concluded that President Barack Obama is in no hurry to put into practice the plans developed by President George W Bush to place 10 missile interceptors in Poland and a mid-course correction radar in the Czech Republic. The Bush administration reached agreements with both governments on such a deployment.
In particular, the Russians will have noted comments made by then President-elect Obama's transition team after Mr Obama spoke to Polish President Lech Kaczynski in November.
After Mr Kaczynski indicated that Mr Obama had said the project would continue, the Obama team issued a statement saying that the president-elect had "made no commitment on it". His position continued to be, the statement said, that he would support deployment if the technology proved workable.
Two key questions coming up are these: will Mr Obama deploy the system and, if he did, would the Russians change their minds and take an active part in it, rather than seeing it as a threat?
"It's too early to say what President Obama will do," said Dr Paul Cornish. "I think it is very unlikely that he will cancel it as a bad Bush idea. The effect in central and eastern Europe in that case would be severe. They are already rattled there by Russian actions in Georgia and over Ukraine.
"But there has always been a question about whether the Russians would be in on this. They have said no in the past. Maybe they will revise their views."
If the Russian move is confirmed, it could also herald a new period of progress in wider strategic arms talks with the US.
Of particular importance is the 1991 Start 1 Treaty, which is due to expire in December this year. Its verification measures provide the basis of mutual monitoring measures, which are used to control other treaties, and these measures will have to be renewed.
In the meantime, plans to develop the anti-missile system continue to progress. The US Missile Defence Agency carried out what it called a "successful intercept" in December. It reported that a "threat-representative target missile" had been launched from Alaska and that an interceptor missile fired from California "intercepted the threat warhead".