Iraq's Prime Minister Nouri al-Maliki on Wednesday rejected U.S. calls for a unity government in the face of a military challenge from al-Qaeda-linked Sunni rebels who have swept large sections of the north and west.
President Obama and Secretary of State John Kerry have both urged Iraqi leaders to broaden the ruling coalition to rise above sectarian and ethnic divisions.
Kerry visited Iraq this week to meet with Iraqi leaders to urge a political realignment.
Such calls represented a "coup against the constitution and an attempt to end the democratic experience," al-Maliki warned in a weekly televised address, the BBC reports.
Al-Maliki, who is Shia, called on "all political forces to reconcile" in the face of a "fierce terrorist onslaught."
Al-Maliki's bloc won 92 of the 328-seats in parliamentary elections in April, but did not claim the overall majority and has been unable to form a coalition government.
The prime minister's remarks come as about half of the 300 U.S. military advisers arrived in Iraq to take up their role of assisting Iraqi security forces.
Kerry's visit this week underscored the sense of urgency created by the military successes of the Sunni extremist group known as the Islamic State in Iraq and Syria (ISIS).
The group has captured Mosul and other large Iraq cities and has vowed to march to Baghdad and the holy Shia cities of Najaf and Karbala.
Kerry also met Tuesday with Masoud Barzani, the president of Iraq's Kurdish autonomous region, and urged him to help form a government in Baghdad. Barzani was non-committal. Kurds, who dominated northern regions of Iraq, have moved increasingly toward seeking their own state.