Washington says the system is needed to counter the threat of missile attacks from "rogue states", including Iran and North Korea but Russia argues that it is a threat to Moscow's security.
 
"We continue to encourage the Russians to partner with us in missile defence and continue our efforts to reassure them that these facilities are not aimed at Russia and could benefit Russia," Gates told reporters in the Czech capital Prague. 

Bush endorsement

The US also offered to allow Russia to maintain a presence at the Czech radar station, to promote transparency. However, Gates said nothing would be agreed without the approval of the Czech government.

"The need for missile defence in Europe is real and I believe it's urgent"

George Bush,
US president
As the defence secretary attempted to assuade Russia's concerns, George Bush, the US president, insisted on Tuesday that the missile shield was vital to ensure the security of the US and its Nato allies from Iran.
   
"The need for missile defence in Europe is real and I believe it's urgent," he said in a policy speech at the National Defense University in Washington. 

"If [Iran] chooses to do so, and the international community does not take steps to prevent it, it is possible Iran could have this capability," Bush said. "And we need to take it seriously, now."

Much of the disagreement between Washington and Moscow over the system has centered on the immediacy of the threat from Iranian missiles on Europe and the US.

Erroneous assessment

Sergey Lavrov, Russian foreign minister, said on a visit to Tokyo that the US initiative was based on an erroneous assessment of the threat posed by Iran.

"North Korea poses a fundamental threat, but Iran does not," he was quoted as telling Masahiko Komura, his Japanese counterpart.
   
Agreement on the system could be delayed after last weekend's election in Poland brought to power a party that has promised tougher negotiations over the plan.

The Czech Republic also said on Tuesday that it might be six months before a deal can be finalised and approved by parliament