It is reviewed activities of the United Nations Security Council as a guarantor of international peace and security with powers to influence infringers of the international law. It is stated that at the beginning of the 21st century, the UN Security Council was powerless to perform its functions and duties to safeguard international peace and security, as well as to resolve a number of large-scale armed conflicts. Therefore, the need to find mechanisms of the UN Security Council reform in order to enhance its effectiveness is proven. It is analyzes options of the UN Security Council reform that member-states of the United Nations started to apply actively in the early 1990s. On the basis of the analysis of the Security Council decision-making mechanism, it is stated that increase in the effectiveness of the UN Security Council can be achieved only by means of the veto right reform. The work analyzes the position of Ukraine, in particular proposals for reformation provided by state officials, as well as analysts, and publicists. It was found that the main obstacle in the reform of veto is the need to persuade five permanent members to limit themselves in the use of the instrument that allows them to influence the entire international system. Therefore, it is unlikely that these states will give their consent to such a reform.