The Shatt al-Arab was considered an important channel for both states' oil exports, and in 1937, Iran and the newly independent Iraq signed a treaty to settle the dispute. In the 1975 Algiers Agreement, Iraq made territorial concessions—including the Shatt al-Arab waterway—in exchange for normalized relations. In return for Iraq recognizing that the frontier on the waterway ran along the entire thalweg, Iran ended its support of Iraq's Kurdish guerrillas.