The States Parties to the present Convention,

Considering the fundamental role of treaties in the history of international relations,

Recognizing the ever-increasing importance of treaties as a source of international law and as a means of developing peaceful co-operation among nations, whatever their constitutional and social systems, Noting that the principles of free consent and of good faith and the pacta sunt servanda rule are universally recognized,

Affirming that disputes concerning treaties, like other international disputes, should be settled by peaceful means and in conformity with the principles of justice and international law,

Recalling the determination of the peoples of the United Nations to establish conditions under which justice and respect for the obligations arising from treaties can be maintained,

Having in mind the principles of international law embodied in the Charter of the United Nations, such as the principles of the equal rights and self-determination of peoples, of the sovereign equality and independence of all States, of non-interference in the domestic affairs of States, of the prohibition of the threat or use of force and of universal respect for, and observance of, human rights and fundamental freedoms for all,

Believing that the codification and progressive development of the law of treaties achieved in the present Convention will promote the purposes of the United Nations set forth in the Charter, namely, the maintenance of international peace and security, the development of friendly relations and the achievement of co-operation among nations,

Affirming that the rules of customary international law will continue to govern questions not regulated by the provisions of the present Convention,