Yet al-Maliki appeared even more isolated as Iraqi politicians, the international community and even Shiite powerhouse Iran rallied behind the new premier-designate as a badly needed unifying figure in the face of a spreading Sunni insurgency.
Al-Maliki, however, raised the specter of further unrest by warning that Sunni militants or Shiite militiamen might don uniforms and try to take control of the streets on the pretext of supporting him.
"This is not allowed because those people, wearing army uniforms and in military vehicles, might take advantage of the situation and move around and make things worse," he told senior army and police commanders.
Al-Abadi's nomination was a major breakthrough in the political deadlock that followed the April parliamentary elections. It shows that al-Maliki — who has demanded that he retain his post as prime minister for a third term since his bloc won most seats in the assembly — has lost some support with the main coalition of Shiite parties.
Top Iranian official Ali Shamkhani also offered his congratulations to al-Abadi, indicating that Iran, with its considerable influence on the Shiite parties, is shifting its backing away from al-Maliki.
U.S. Secretary of State John Kerry on Tuesday urged al-Abadi to work quickly to form an inclusive government and said the U.S. is prepared to offer it significant additional aid in the fight against Islamic State militants.
President Barack Obama called al-Abadi's nomination a "promising step forward" and urged "all Iraqi political leaders to work peacefully through the political process."
The U.S. has already increased its role in fighting back the Sunni extremists who have threatened the autonomous Kurdish region in northern Iraq. Senior American officials said Monday that U.S. intelligence agencies are directly arming the Kurds who are battling the militants — a major policy shift after years of just working with the central government.
On Tuesday, a U.S. drone strike destroyed a militant mortar position threatening Kurdish forces defending refugees near the Syrian border.
The U.S. airstrikes, which began last week, have reinvigorated Iraqi Kurdish forces battling the Islamic State. On Sunday, the Kurdish fighters retook two towns from the Sunni militants in what was one of their first victories after weeks of retreat. But in the eastern Diyala province, Kurdish forces were driven out on Monday from the town of Jalula after fierce fighting with the militants.
An Iraqi military helicopter providing aid to civilians fleeing the militants crashed in near the Sinjar mountains in northern Iraq, killing the pilot, army spokesman Qassim al-Moussawi said in the statement. The helicopter crashed after too many civilians attempted to board it.
The New York Times reported on its website that reporter Alissa J. Rubin, riding along on the helicopter for a story, suffered an apparent concussion and broken wrists in the crash.
The European Union said Tuesday it wants to "bring vital assistance to hundreds of thousands of Iraqi civilians trapped by the fighting" and was increasing its aid by 5 million euros ($7 million) to a new total of about $23 million for this year.
EU Aid Commissioner Kristalina Georgieva said the funding will help "vulnerable Iraqis, including the minority groups besieged in the mountains of Sinjar" and the communities hosting a growing number of refugees.
In violence, Tuesday, a car bomb exploded in the Shiite neighborhood of Zafaraniya, killing four people and wounding 13 others, said police, while another detonated in the commercial district of Karradah, resulting in 11 dead and 28 wounded. The Karradah blast was about 200 meters from al-Abadi's hosue. But the intent of the blast is not immediately clear.