MOSCOW, May 14 (Xinhua) -- Russia will seek to maintain nuclear parity with the United States, said the country's national security strategy until 2020 released on Wednesday.

　　If the United States deploys a global missile defense system and pursues the prompt global strike concept, Russia will "make every effort to retain parity with the United States in the field of strategic offensive weapons in the most cost-effective way," the strategy paper said.

　　In the long-term perspective, Russia needs to safeguard strategic stability so as to gain favorable conditions for its steady development, the document said.

　　Russia complies with "principles of maintaining stability and predictability in the area of strategic offensive weapons and attaches special significance to achieving new full-format bilateral agreements on continued reduction and limitation of strategic offensive weapons," it said.

　　The paper also confirmed Russia's commitment to a world free from nuclear weapons, and stated that Russia was ready to discuss the reduction of conventional weapons.

　　The strategy document, approved by Russian President Dmitry Medvedev on Tuesday, listed top challenges to national security and outlined government priorities through 2020.