US President George W Bush insisted today a missile shield in Europe was needed for the security of the United States and its NATO allies.
"The need for missile defense in Europe is real and I believe it's urgent," Mr Bush said in a policy speech at the National Defense University in Washington.
Washington's plans to locate components of the anti-missile system in Poland and the Czech Republic have angered Moscow, leading to strains between the two countries that have revived memories of the Cold War.
Mr Bush said the missile system was intended as protection against attacks from Iran and other countries that the United States views as "rogue states." He said the system was not a threat to Russia.
US intelligence agencies assess that with continued foreign assistance, Iran could develop an intercontinental ballistic missile capable of reaching the United States and all of Europe before 2015, Mr Bush said.
"If it chooses to do so and the international community does not take steps to prevent it, it is possible Iran could have this capability and we need to take it seriously, now," Mr Bush said.
Mr Bush defended the missile defense system even as his top aides were trying to soothe Russia's concerns. US officials and NATO envoys earlier discussed an offer to keep parts of the missile shield on "stand-by" short of full readiness as part of a way to bridge differences with Russia.
US Defense Secretary Robert Gates, on a visit to Prague, said Washington may delay activation of components of the anti-missile system in the Czech Republic and Poland if Russia cooperates.