In order to reassure anti-imperialist elements on the eve of declaring war on Spain, Congress adopted a measure pledging that the United States had no designs on remaining in Cuba following conclusion of the conflict. Senator Henry M. Teller of Colorado drafted an amendment to the resolution of war, which stated that the United States "hereby disclaims any disposition of intention to exercise sovereignty, jurisdiction, or control over said island except for pacification thereof, and asserts its determination, when that is accomplished, to leave the government and control of the island to its people.” The United States did not, as pledged, annex Cuba. Occupation continued until 1902 when the Platt Amendment was inserted into the Cuban constitution in return for the withdrawal of American forces. In 1903, the U.S. also secured rights to maintain a naval base at Guantánamo Bay, one of the world`s great harbors, located at the southeastern tip of Cuba. American rights were reconfirmed in a formal treaty in 1934, an agreement that cannot be rescinded without mutual consent.