Iraq’s three-member presidential council on Thursday approved a security pact with the United States setting out a three-year timeframe for the full withdrawal of American troops, a spokesman said.

The panel’s decision marked the final step for the agreement to replace a U.N. mandate that expires on Dec. 31.

Iraq’s parliament signed off on the deal last week following months of tough talks between U.S. and Iraqi negotiators that at times seemed on the point of collapse. The entire process has been fraught with hardscrabble dealmaking between ethnic and sectarian groups.

President Jalal Talabani, a Kurd, and his two deputies Tariq al-Hashemi, a Sunni Arab, and Adel Abdul-Mahdi, a Shiite, signed the accord at their headquarters in Baghdad, council spokesman Nasser al-Ani told The Associated Press.

The agreement provides a legal basis for American troops in Iraq after the expiration of the U.N. mandate, but it includes the caveat that it should go before voters in a referendum to be held by the end of July.

Under the deal, U.S. forces will withdraw from Iraqi cities by June 30 and the entire country by Jan. 1, 2012.

Iraq also will gain strict oversight over the nearly 150,000 American troops now on the ground, representing a step toward full sovereignty for Iraq and a shift from the sense of frustration and humiliation that many Iraqis feel at the presence of American troops on their soil for so many years.

Followers of anti-U.S. cleric Muqtada al-Sadr opposed the measure, demanding an immediate withdrawal, and the Shiite leader has called for peaceful protests against the continued presence of American forces in Iraq.