"There is a chance for strengthening Europe's security with special attention given to Poland," Prime Minister Donald Tusk said.

Obama shelved the Bush-era plan for missile defense sites in Poland and the Czech Republic on Thursday, saying a new, redesigned defensive system would be cheaper, quicker and more effective against the threat from Iranian missiles.

Tusk said that Obama's "proposal of an alternative strategy should not affect the security of Poland" or of Europe.

"I would not describe what is going on today as a defeat for Poland," Tusk told reporters, adding that he spoke to Obama on Thursday and the U.S. leader signaled to him that "Poland has a chance to win an exclusive position" in the new system.

Polish and Czech leaders long saw former President George W. Bush's plan as a way to cement military links with the U.S. and protect the region against an increasingly self-confident Russia. The U.S. has always stressed that the system was not in any way aimed at Russia.

The decision to abandon the Bush administration's plans for a land-based missile defense system in Eastern Europe came about because of a change in the U.S. perception of the threat posed by Iran, U.S. Defense Secretary Robert Gates said.

The U.S. has concluded that Iran is less focused on developing the long-range missiles for which the system was originally developed, making the building of an expensive new shield unnecessary. New technology also has arisen that military advisers decided could be deployed sooner and more effectively, Obama said.

Gates said the new system could result in missiles being placed on land in Eastern Europe in 2015.