WASHINGTON, D.C./BAGHDAD – On Thursday, U.S. forces were targeted in three attacks in Iraq but suffered no casualties, security sources have said, in the most geographically widespread series of strikes on U.S. assets in a single day since the Israel-Hamas conflict started.

A defective drone in Iraq may have helped keep America from being dragged deeper into a widening Middle East conflict.

The drone, which was launched at the Erbil air base by an Iranian-backed militia before sunrise on Oct. 26, penetrated U.S. air defenses and crashed into the second floor of the barracks housing American troops at about 5 a.m., according to two U.S. officials familiar with the matter.

But the device laden with explosives failed to detonate and in the end only one service member suffered a concussion from the impact, said the officials, who asked to remain anonymous to speak freely about the attack. The U.S. had got lucky, they added, as the drone could have caused carnage had it exploded.

The incident was among at least 40 separate drone and rocket attacks that have been launched at U.S. forces by Iranian-backed militias in Iraq and Syria over the past three weeks in response to American support for Israel in the Gaza war, according to Pentagon data and the two U.S. officials.

The bombardment has only caused a few dozen minor injuries so far, with many of the rockets and one-way attack drones intercepted by U.S. air defenses in Iraq and Syria, where a total of 3,400 American troops are based.

David Schenker, a former U.S. assistant secretary of state at the Washington Institute for Near East Policy think tank, cautioned that while neither Iran and its allied groups nor the U.S. appeared to want a direct confrontation, the risks were growing. The possibility of a major strike that draws America into a conflict is “a very realistic concern,” he said.

“I think they are calibrating the attacks to harass rather than kill en masse U.S. troops,” he said of Iraqi and Syrian militias. “But there’s a lot more they can do.”

It’s unclear how President Biden would respond to a major attack that kills a large number of Americans. Struggling in opinion polls ahead of next year’s presidential election, Biden has so far sought to limit the U.S. role in the conflict mostly to ensuring military aid to Israel.

On Sunday, Secretary of State Antony Blinken flew to Iraq — where most of the attacks on U.S. forces have taken place — to push Iraqi Prime Minister Mohammed Shia Al-Sudani to crack down on the militias operating there and avert any escalation.

Yet Sudani has had little luck in persuading the militia groups from letting up their assault, or convincing their bankrollers in Iran to rein them in, according to five senior lawmakers in Sudani’s governing coalition, a security adviser to the premier and a militia commander.

On Sunday, Secretary of State Antony Blinken flew to Iraq — where most of the attacks on U.S. forces have taken place — to push Iraqi Prime Minister Mohammed Shia Al-Sudani to crack down on the militias operating there and avert any escalation.

The prime minister and around 10 senior members of his government met with the commanders of about a dozen militia groups in Baghdad on Oct. 23 to press the groups to halt their attacks on U.S. forces, said the seven people, who were either present or were briefed on the meeting.

The plea largely fell on deaf ears, though, with most of the commanders vowing to keep up their assault until Israeli forces ended their siege and bombardment of the Gaza Strip, they added.

“No one — not the prime minister or anyone else — can stand against our religious duty,” said Ali Turki, a Shi’a lawmaker in the governing coalition as well as a commander with the powerful Iranian-backed Asaib Ahl al-Haq militia.

Arif al-Hamami, another Shi’a lawmaker, said the prospects for diplomacy looked bleak.

“I don’t think that the prime minister has the power to stop the attacks as long as Israel is committing atrocities in Gaza with American help.”

Iraq’s prime minister has limited control over the militias, whose support he needed to win power a year ago and now form a powerful bloc in his governing coalition. The militant groups, which proliferated in Iraq in the wake of the U.S.-led invasion in 2003 that toppled Saddam Hussein and his government, are trained and funded by Iran.

For Sudani, it’s been a case of shuttle-diplomacy.

Hours after meeting Blinken on Sunday, the premier flew to Tehran to directly appeal to Supreme Leader Ayatollah Ali Khamenei and other Iranian officials for help, according to a senior Iraqi politician close to the prime minister who was briefed on the visit.

Sudani asked the Iranian officials to pressure the militias into halting their attacks on U.S. forces in Iraq, fearing his politically and economically unstable country could ill afford an escalation that would see the Americans strike back against the militants, the politician said.

The officials told him that the militias in Iraq made their own decisions and Tehran wouldn’t interfere in the situation there, the politician added.

Iran has decried the retaliatory Israeli assault on Gaza as a genocide and warned that if it isn’t halted, the U.S. will not be “spared from this fire.” Meanwhile, the Hezbollah movement backed by Tehran in Lebanon — a group that sources say has acquired powerful Russian anti-ship missiles — has warned Washington that it would pay a heavy price in a regional war.

The response by Biden has been cautious so far; he ordered overnight strikes on two Iranian-linked arms storage facilities in Syria last month while they were unoccupied, but has not ordered any strikes in Iraq. On Wednesday, Biden followed up with a similar strike in Syria and U.S. Defense Secretary Lloyd Austin cautioned, “We urge against any escalation.”

Biden has warned Iranian-backed groups across the region, including the strong Hezbollah movement in Lebanon, against expanding the conflict, but he and other officials have declined to be explicit about what they would do in response.

The U.S. hopes a military show of force will dissuade any serious attack and has deployed two aircraft carrier strike groups and even taken the rare step over the weekend of announcing that an Ohio-class submarine had moved to the region.

The response to the crisis from Biden, a Democrat, hasn’t been strong enough for many of his critics, including Republicans in Congress.

“They are laughing at us in Tehran,” said Republican Senator Tom Cotton, a member of the Senate Armed Services Committee. “Iran will continue to target Americans until President Biden gets serious about imposing severe costs on Iran.”

–Excerpts from a Reuters report. Edited for style and space.