An anti-American cleric in Iraq has called on his followers to stop their attacks on U.S. troops because he does not want the Americans to have an excuse to remain in the country.

Shi'ite cleric Muqtada al-Sadr said in a statement on his website late Saturday that he has ordered his militias to let the Americans leave peacefully. However, Sadr warned that he will step up attacks against the U.S. forces if any stay past the end of the year.

Fewer than 50,000 U.S. troops remain in Iraq, all of whom are set to withdraw by the end of this year. However, Iraq's political leaders are currently negotiating with the United States on whether to keep some U.S. military personnel on as trainers beyond 2011.

U.S. and Iraqi officials have said Iraqi forces are capable of maintaining internal security, but need training in using heavy weaponry to defend the country's borders, airspace and territorial waters.

Sadr's Mahdi Army militia fought U.S. troops in Iraq until 2008 when he disbanded the force and focused his movement on Iraq's political process. His Sadrist party is a key faction in Prime Minister Nouri al-Maliki's coalition government.