A contract between two independent, sovereign political entities (such as the United States or France). The president has the authority to negotiate treaties with other countries, but the treaty cannot go into effect until it is approved by a two-thirds vote of the Senate.Senators can amend a treaty (change its wording) or enact reservations (change its interpretation) by a simple majority, which enables them to build a consensus to achieve a two-thirds vote.
The United States Constitution, What It Says, What It Means, A Hip Pocket Guide