Moscow says it will neutralise the US system with short-range missiles
Russia's foreign minister has said it will abandon plans to station missiles in Kaliningrad if the US does not base part of a missile shield in Europe.
Sergei Lavrov said short-range Iskander missiles would only be deployed in the western enclave, which borders Poland, to neutralise any perceived US threat.
President Dmitri Medvedev unveiled the planned counter-measure a week ago.
The US insists the planned shield is designed solely to guard against attack by "rogue states", such as Iran.
At present, the system will include a tracking radar in the Czech Republic and 10 missile interceptors in northern Poland. Moscow says they could threaten its own defences.
These would be in addition to radars and interceptors in Alaska and California in the US, and another radar at Fylingdales in the UK.
At a news conference in Moscow on Tuesday, Mr Lavrov was asked whether the Russian plans to deploy Iskander missile systems in Kaliningrad might affect Friday's EU-Russia summit and renewed talks on a new partnership and co-operation agreement.
The US plans a global missile shield to protect against "rogue states"
"I don't see any connection between what was announced in the message of our president to the Federal Assembly and relations between Russia and the European Union," he said.
"We said… that if the third zone of positioning of the US anti-missile shield is created, one of the measures to neutralise the threats to Russia's security that would inevitably arise will be the deployment of Iskander missile systems in the Kaliningrad region."
The Iskander systems would therefore be deployed "only if the third zone of positioning really takes shape", Mr Lavrov added.
EU leaders warned Russia on Friday that the decision to base missiles in Kaliningrad would not contribute to creating a climate of confidence or to the improvement of security.
On Saturday, a senior aide to US President-elect Barack Obama said he had "made no commitment" to go ahead with plans to base the interceptors in Poland, despite an earlier statement by the Polish president saying that he had made such a promise.