Iraqi Shi'ite cleric Moqtada al-Sadr said on Monday he was willing to work with Iran-backed militia groups - his political rivals - to end the United States military presence in Iraq through political and legal means.

If that does not work, he will "take other actions" in cooperation with his rivals to kick out U.S. troops. Sadr's militia fought U.S. troops for years following Washington's invasion and toppling of Saddam Hussein in 2003.

Sadr, who portrays himself a nationalist rejecting both Iranian and U.S. influence, called in a statement on Iran-backed militias to avoid "irresponsible actions" that can be used to justify attacks on Iraq.