Guantanamo Bay Naval Base is locate on the shore of Guantánamo Bay at the southeastern end of Cuba and has been used by the United States Navy for more than a century. It is the oldest overseas U.S. Navy Base and the only one in a country with which the United States does not have diplomatic relations. The United States controls the land on both sides of the southern part of Guantánamo Bay (Bahía de Guantánamo in Spanish) under a lease set up in the wake of the 1898 Spanish-American War. The lease was established in a 1903 agreement between the two governments, and its terms were modified in a 1934 treaty. The current Cuban government considers the U.S. presence in Guantánamo to be an illegal occupation of the area, and argues that the Cuban-American Treaty, which established the lease in 1903, now violates article 52 of the 1969 Vienna Convention on the Law of Treaties. However, Article 4 of the same document states that the Vienna Convention on the Law of Treaties shall not be retroactively applied to any treaties made before it. The U.S. also argues that its right to the base have been reaffirmed by Cuba since the original treaty.