The Czech government has confirmed that America has abandoned George W Bush's commitment to build a missile defence system in central Europe.
President Bush had said the system was an essential protection against rogue states attacking Europe with a nuclear-armed missile.
Critics of the Obama administration are suggesting that persistent Russian opposition to the plan is the explanation. Other theories include the enormous expense at a time when the American budget deficit is growing sharply and also continuing concerns that a missile defence system - first proposed by President Reagan in the early 1980s - is technologically too difficult. Some believe that a dirty nuclear bomb - smuggled into a major urban centre in a 'suitcase' - is much more likely and a missile defence system offers no protection against it.
Obama administration officials are claiming that the policy shift reflects their belief that Iran's long-range missile plans are less advanced than originally predicted.
Nile Gardiner of Washington's Heritage Foundation is in no doubt that the White House has been intimidated by the Kremlin:
"This is bad news for all who care about the US commitment to the transatlantic alliance and the defence of Europe as well as the United States. It represents the appalling appeasement of Russian aggression and a willingness to sacrifice American allies on the altar of political expediency. A deal with the Russians to cancel missile defence installations sends a clear message that even Washington can be intimidated by the Russian bear."
Last November Russia moved its own ballistic missiles to Kaliningrad between Nato member states Lithuania and Poland. Russian President Dmitry Medvedev had threatened to "neutralise - if necessary - the [US] anti-missile system".
Last week Russia shut the door to tougher sanctions against Iran. It may be that this U-turn reflects a hope by Washington to trade the missile defence system for Russia pressurising Tehran. Time will tell.
The Wall Street Journal has an informative background report on this developing story.
