The United Nations was established so that it could resolve conflicts between nations by : launching military attacks. forming blockades. imposing sanctions. occupying border countries.
My answer would be imposing sanctions. When sanctions are imposed on a country it can hurt it both politically and economically. This is true when member countries give their full support to U.N. sanctions. A good example would be when South Africa still practiced Apartheid. Because most countries didn’t support that policy, they withdrew their support and South Africa was isolated for a long time.