Agreement between the US & Poland to allow parts of a US anti-missile shield to be built on Polish soil is expected by October.
Deputy Polish Foreign Minister Witold Waszczykowski, who is visiting Washington to negotiate terms for hosting parts of the installation, said that a deal should be signed in September or October.
Mr Waszczykowski claimed the deal should strengthen Poland's security.
Warsaw has been lobbying for a political and security pact between the two NATO states as a main condition for hosting the missile interceptor site.
The plan to place interceptors in Poland and a radar system in the Czech Republic has led to a row with Russia.
Russian President Vladimir Putin has threatened to aim missiles at targets in Europe if the US goes ahead with its plan.
Washington says its installation will guard against attacks from 'rogue states' such as North Korea or Iran.
But Moscow says the scheme will upset the post-Cold War strategic balance and is really aimed at its military capability.
