But the timing of the announcement is regarded as disastrous by the Poles. Eugeniusz Smolar, a former chief of Warsaw's Centre for International Relations, said: "We are disappointed." But he added that the Polish government had been assured by the Americans that promises of training with Patriot missile batteries and help in modernising the Polish military remained valid.

A few weeks ago, in a cri de coeur to Washington, several senior eastern European officials and public figures wrote a public letter to Obama complaining that their security interests were being ignored by the west to improve relations with Moscow.

Rasmussen, in his first big speech, is to call tomorrow for a new relationship between the western military alliance and Russia, taking more account of Moscow's security and strategic interests.

Russian experts said Obama's decision could only be seen as an unambiguous concession to Moscow, adding that it would severely disappoint the new Nato countries of eastern Europe. Yevgeny Miasnikov, a senior research scientist at Moscow's Centre for Arms Control, said the US administration would now consider ways of assuaging the Poles and Czechs, which might include providing Poland with Patriot interceptors capable of shooting down short- and medium-range missiles.

"Obama has taken a step in the direction of improving US-Russian relations. This will definitely help build a partnership," Miasnikov said. "Russia will also now make some concessions, maybe on strategic talks over nuclear arms reduction or maybe over Iran.