Iraq's president named a new prime minister to end Nouri al-Maliki's eight-year rule on Monday, but the veteran leader refused to go after deploying militias and special forces on the streets, creating a dangerous political showdown in Baghdad.

Washington, which helped install al-Maliki following its 2003 invasion that toppled Saddam Hussein, congratulated Haidar al-Abadi, a former al-Maliki lieutenant who was named by President Fouad Masoum to replace him.

Al-Maliki said in a televised speech the that president's decision to name a replacement for him was a "dangerous violation" of the constitution and, flanked by political allies, he vowed "we will fix the mistake."