The article explores the aspects of the interaction between the USSR and the USA on the Mongolian question within the UN during first 15 years of the Cold war. The author dwells such problems as Mongolia’s contribution to the war against Japanese militarism; the question of the involvement of Ulaanbaatar to the Korean war in 1950-1953; the arguments between Moscow and Washington concerning the package admittance of new members; the reason of the veto power exercised by the Chiang Kai-shek regime; ideological conflicts between two opposing blocs in the United Nations. The first application for Mongolia’s admission to the UN was submitted to Secretary-General Trygve Lie in a letter dated June 21, 1946, signed by Kh. Choibalsan, Prime-Minister...