BAGHDAD — Iran endorsed Iraq’s new prime minister-designate on Tuesday, striking a death blow for incumbent Nouri al-Maliki as a wide spectrum of domestic factions – and even his most loyal militia – also turned their backs on the country’s longtime leader.

Maliki’s growing isolation raised hopes of a relatively smooth transfer of power after a tense two-day standoff during which the desperate incumbent deployed security forces to strategic points across the capital.

The Iranian leadership, which wields significant influence in Iraqi politics, joined a range of Iraqi political groups – including Kurds, Sunnis and Shiites – in backing Shiite politician Haider al-Abadi’s efforts to form a new government.

The United States and many Iraqis see the creation of a new, more inclusive government as crucial in peeling away support for the Sunni extremists of the Islamic State. Maliki, a Shiite, had marginalized the country’s Sunni minority, pushing some to support the fighters.

The al-Qaida-inspired militants have seized large chunks of territory in recent weeks to form a renegade nation stretching across the Iraqi border into Syria. The sweeping offensive has forced tens of thousands of Iraqis – many who are members of religious minorities – to flee for their lives.

On Tuesday, U.S. Defense Secretary Chuck Hagel announced that an additional 130 U.S. troops had arrived in Iraq to help plan for a likely expansion of humanitarian relief operations in the north.

Although Hagel did not give details, he signaled that the Pentagon was laying the groundwork for a more ambitious rescue mission. Speaking to Marines at Camp Pendleton, California, Hagel said the extra troops would “take a closer look and give a more in-depth assessment” of the U.S. relief efforts that began last week.

The new deployment comes in addition to 775 troops previously authorized to go to Iraq to protect U.S. diplomatic facilities, work with Iraqi forces and conduct other missions.

The U.S. government has been conducting airstrikes against the Sunni extremists in the country’s north, where the semiautonomous Kurdish region has been pleading for support to keep Islamic State fighters from overrunning its boundaries.

The United States has also begun directly supplying the Kurds with weapons, U.S. officials said this week. Britain has agreed to transport military supplies “from other contributing states” to Kurdish forces so they can “provide effective protection” to refugees fleeing Islamic State militants, a spokesman for the British prime minister’s office said on Tuesday, speaking on the usual condition of anonymity.

There were indications that other European countries also might start providing military aid to the Kurds or other Iraqi forces. On Tuesday, the German Defense Ministry said it was “examining” whether it should deliver non-lethal military equipment to Iraq’s armed forces.

The U.S. relief mission has been limited to airdrops of food, water and medical supplies to thousands of desperate members of the Yazidi faith who have sought refuge on a mountain after the northwestern town of Sinjar was stormed by the extremists on Aug. 3.