Poland is buying the Patriot air defense system from the United States and will begin negotiations for it in Washington next month.

The decision, announced Tuesday by top government officials, has been spurred by the deteriorating security situation in Eastern Europe resulting from Russia's annexation of the Crimea from Ukraine and continued Russian-supported rebellion in eastern Ukraine.

"One of the top priorities of my presidency is security ... and defense issues, with a particular emphasis on the modernization of the Polish armed forces ... especially "In the dangerous world, and where there is a regression in the level of security due to the Russian-Ukrainian conflict, said President Bronislaw Komorowski.

"For technical modernization, and for Polish defense against potential threats to be effective, the priority of priorities has become missile defense."

The president said Poland's Deputy Prime Minister and Defense Minister Thomas Siemoniak would travel to Washington next month to to quickly conclude a contract to purchase the system through the U.S. Foreign Military Sales program.

The deal would be worth more than $5 billion.

The Patriot system, made by Raytheon, will be part of a modernization program called Vistula.

Additional arms procurement projects would be announced in the near future, he said.