Global security directly depends on defense spending. The North Atlantic Treaty Organization (NATO) forms a system of collective security, but at the same time it does not have its own armed forces. The article examines the basic principles of NATO’s functioning (indirect contributions – expenditures of the member states of the Alliance, which constitute the most significant part of the funding; direct contributions to support budgets and finance the development of capabilities and the implementation of programs that allow the Alliance to work on achieving its goals and priorities; contributions to NATO budgets according to an agreed distribution key based on their gross national income). It has been established that the target indicator for the amount of the contribution to the defense budget of the Alliance is 2 % of the GDP of a NATO member state. Analysis of the defense expenditures of the vast majority of the Alliance members showed their significant growth, however, according to the level of achievement of the target indicator, they can be divided into the following groups: those that have already reached 2 % of GDP or almost reached this level; those who are rapidly moving towards the target indicator and anticipate its achievement in the near future; those who plan to reach the target level of defense spending in the long term, but currently have an indicator below 1,5 %. Dissatisfaction of the United States of America, as the country that has financed NATO the most for many years, with the dynamics of achieving the target indicator by other member countries, causes a number of problems and controversies, in particular, with regard to the exit of this or that country from the Alliance or the hypothetical termination of its functioning as a whole.