Russia's military is ready to "neutralise" any threat to its nuclear deterrent from US missile defence sites in Europe, Deputy Foreign Minister Sergei Kislyak said Monday, according to Interfax news agency.

"If we see the development of systems that could reduce our deterrent potential, our military will have to take steps to neutralise the threat," Kislyak was quoted as saying at a briefing in Moscow.

He did not specify the steps that would be taken, saying "this will be decided by military specialists."

"We would prefer not to have to do this," he added.

Kislyak said US proposals to ease Russian concerns about the missile shield, which Washington claims is aimed at countering possible threats from states such as Iran, remained in doubt.

US Defence Secretary Robert Gates and Secretary of State Condoleezza Rice visited Moscow in March and offered Russia the opportunity to monitor the sites, which they plan to install in the Czech Republic and Poland, but Czech and Polish officials later cast doubt on that offer.

"There are misunderstandings between what the US foreign and defence ministers said here (in Moscow) and what their Czech and Polish partners say. So this still remains in question," Kislyak said.