White House Press Secretary Dana Perino said Thursday that the United States and Poland reached an agreement on a missile defense deal.

Perino said the two countries initialed an agreement that is being reviewed, but declined to say when the final signing would take place. During a press briefing with reporters, Perino said the U.S. welcomes the development, and added that missile defense would be an addition to the security that NATO currently provides.

When asked about concerns over the U.S. relationship with Russia, Perino said President Bush has spoken to Russian President Dmitry Medvedev and Prime Minister Vladimir Putin — assuring both leaders that the missile defense shield is in no way aimed at Russia. The purpose of the shield, Perino said, is to protect European allies.

When a reporter said the timing of the announcement is curious, given the situation in Georgia, Perino replied by saying the U.S. and Poland have been nearing agreement for "quite some time" — noting that the U.S. recently finished a similar deal with the Czech Republic.

Perino added that she could not say whether the actions of the last several days spurred final action on the deal with Poland. She added that the U.S. thinks it is important for the Polish Armed Services to be modernized.

FOX News' Kelly Chernenkoff contributed to this report.