Diplomats and military officials said Biden’s bigger goal is to reduce hostilities between the United States and Iran and its representatives in the region, including Iraq, and to seek a way back to diplomacy with Tehran. This week the United States opened new negotiations with Iran to curtail its nuclear program.

The rapprochement comes because the Biden government is simultaneously staring at deadly militias in Iraq that officials believe are acting with Tehran’s aid and perhaps orders. Attacks by Iran or its proxies on Americans could undermine the broader diplomatic aim, officials said.

They could also turn on its head a new attempt by the United States to convince Iraq to turn away from Iran – without expecting to break its spiritual, economic, and cultural ties – by offering incentives instead of threats.

“So that America can pursue our values ​​and interests worldwide, we have to get involved in the world,” said Ned Price, the spokesman for the State Department, after the attack in Erbil. “And of course there are additional risks involved in some parts of the world.”

So far, according to two senior Defense Department officials, there has been no extensive discussion in the Pentagon Central Command about a specific military response to the strike in Erbil on Monday as the US and Iraqi authorities investigate who launched the attack. Both Mr Blinken and Defense Secretary Lloyd J. Austin III, who have completed three combat tours in Iraq, have spoken to their Iraqi counterparts to offer assistance with the investigation.

Officials blame Iranian militias such as Kataib Hezbollah and Asa’ib Ahl al-Haq, who have been responsible for similar previous strikes, the Erbil missiles. But officials from the White House, State Department and Pentagon have stopped making specific allegations.

“What an important test for the new government,” said Simone Ledeen, the Pentagon’s chief administrative officer until last month, on Twitter on Monday. “Will be interested to see if there is an answer.”

Iraqis have long been suspicious of American officials who, after ordering a military invasion in 2003 and the ousting of Saddam Hussein, are still held responsible for the security vacuum that followed the disintegration of the Iraqi army by the US occupation authorities. Anger at the United States rose again last month when the Trump administration pardoned four American security companies for their roles in the 2007 massacre of 17 Iraqi civilians in Nisour Square, Baghdad.

As Vice President during the Obama administration, Mr. Biden was among those who oversaw the end of the American-led Iraq war and the withdrawal of the last 50,000 combat troops in 2011, only to be surprised by the rise of Islamic State two years later.

Officials said Mr Biden has a deeply personal interest in Iraq, where his son Beau served in the Army National Guard and was exposed to toxic cremation pits that may have led to the brain tumor that killed him in 2015.

His Secretary of State, Mr Blinken, has begun what a senior State Department official on Friday referred to as a review of American policy in Iraq that will allow for a change in approach. The review will include feedback from the Pentagon before it goes to the White House, possibly as early as next month.

The government is considering bringing hundreds of diplomats, security guards and contractors back to the embassy in Baghdad. At a time of mounting tension with Iran, the numbers were reduced in May 2019, which has resulted in a fluctuating workforce since then.

The State Department is not yet ready to reopen its consulate in the southern Iraqi city of Basra, an important wiretapping post near the Iranian border, which the Trump administration closed in September 2018 after militias left the airport area where it was stationed had been shot in the air. Nobody was injured in this attack.

The department is also looking into expanding the limits the Trump administration has placed on how much power the Iraqi government can buy from Iran – an agreement that critics warn could fund Tehran’s aggression but provides a lifeline for millions of people that would otherwise get by without electricity.

Iraqi bank officials met with American diplomats this week on the issue, which is currently forcing Baghdad to ask Washington to stop buying energy every few months without imposing sanctions.

Two other government officials from Biden said the US Agency for International Development is also considering sending more humanitarian aid to parts of Iraq, mainly to the western and northern regions of the country hardest hit by the Islamic State.

But several Pentagon officials and senior military officers said it was unclear what the Biden team’s red lines look like when it comes to protecting American personnel in Iraq from Iran or its proxies.

Following a rocket attack that killed an American contractor in December 2019, the United States blamed Kataib Hezbollah and bombed five of its bases. This resulted in a siege of the U.S. embassy, ​​with protesters detaining diplomats in the extensive grounds for two days, and prompted Mr Trump to order a military strike that killed Iran’s most revered general while visiting Baghdad .

David Schenker, Trump’s deputy undersecretary of state for Middle East policy, said it was the responsibility of the Shiite-led Iraqi government to curtail Iranian-backed militias.

“I don’t think you’ll behave better in Iraq if you slander Iran,” said Schenker, now a senior fellow at the Washington Institute for Middle East Policy, in an interview. “Ultimately, it’s all about Iran – the missiles, the weapons, the funding and the direction all come from Tehran.”

Military officials say 14 107-millimeter rockets were fired in the Erbil attack, but six failed. The attack on territories controlled by Kurdish forces has raised concerns about security vulnerabilities in what is considered the safest region of Iraq.

A little-known group known as Awliya al Dam or Guardians of the Blood assumed responsibility for the attack but did not provide any evidence. The group assumed responsibility for two bomb attacks on US military convoys last August.

An anti-rocket system was in place and operating at Erbil airport at the time of the attack, but the missiles landed in an area not covered by the system, an American military official said.

U.S. commanders said the 2,500 troops now residing in Iraq – roughly half the number from last summer – would not only be enough to act as a bulwark against Iranian proxies and other influences, but also to help Iraqi security forces find out remaining Islamic bags to help state fighters.

The Secretary General of the Organization of the North Atlantic Treaty, Jens Stoltenberg, announced on Thursday that it would increase its military mission in Iraq from 500 employees to 4,000 soldiers and expand training beyond Baghdad.

Jane Arraf reported from Amman, Jordan.