Polish President Lech Kaczynski has said parts of a US missile defence system will be built in Poland despite fierce Russian objections to the plan.
Mr Kaczynski said the missile defence plan was good for Poland
After talks with US President George W Bush, Mr Kaczynski said it was "a foregone conclusion" that interceptor missiles would be based in Poland.
Mr Kaczynski tried to reassure Moscow that the plan was not aimed at Russia.
Russia has threatened to point missiles at Europe if the US stations parts of a new missile shield near its borders.
"The shield will exist because for Poland this will be a very good thing," Mr Kaczynski said after talks with Mr Bush in Washington.
He said the missile defence plan was aimed at the "defence of our democracies against the countries who might have or already do have nuclear weapons or weapons of mass destruction".
Mr Bush called the plan a "symbol of our desire to work for peace and security".
The US has said the facilities would not be directed at Russia, but at "rogue" states such as North Korea and Iran.
Nato signed on to the plan after it was expanded to include the alliance's flank in south-eastern Europe.
Russia is particularly opposed to US plans to site a radar in Czech Republic and 10 anti-missile interceptors in Poland and has warned the system could spark a new arms race.
On Saturday, Russian President Vladimir Putin gave notice that his country was suspending its application of a 1990 treaty limiting conventional weapons in Europe.
Moscow has also voiced opposition to Nato's possible further eastward expansion to include more former Soviet states, such as Ukraine and Georgia.