ABDULJABBAR ZEYAD/Reuters The site of a Saudi-led air strike in the Red Sea port city of Hodeidah, Yemen, on Sept. 22, 2016.

WASHINGTON — U.S. partners are almost certainly committing war crimes in the ongoing conflict in Yemen, a U.S. congressman argued in a letter to Secretary of State John Kerry.

“The frequency and scale of the civilian killings by the Saudi military coalition make it difficult to come to any conclusion other than that war crimes have been and are continuing to be committed in Yemen,” Rep. Ted Lieu (D-Calif.) wrote on Tuesday. He argued that any U.S. role in the violence, even an indirect one, makes the country liable for the more than 10,000 people killed there in the last 18 months.

“The U.S. needs to cease immediately the aiding and abetting of the coalition,” Lieu wrote.

In March 2015, President Barack Obama ordered the U.S. military to begin supporting the Saudi-led coalition, which seeks to restore the Saudi-friendly Yemeni government after a rebellion by Iran-backed militants known for their own brutal tactics. The U.S. has since been providing jet fuel, intelligence and fresh arms supplies to the coalition.

Lieu and several other lawmakers have spent months condemning the U.S. role in the conflict, but little has changed. On Saturday, the Saudi-led campaign launched one of its deadliest attacks on Yemen yet with a series of airstrikes that killed at least 140 civilians and wounded hundreds more.

Lieu decided to write again after a Reuters investigation showed that State Department lawyers knew the U.S. could be responsible for war crimes in Yemen. U.S. officials could be prosecuted for their role in the campaign under international and U.S. law, Lieu suggested.

“Every U.S. assisted bomb that kills children, doctors, patients, newlyweds and funeral mourners has the potential to amplify hatred toward the U.S,” he added, describing such hatred as helpful for extremist recruiting.

He implored the U.S. to halt all assistance to the Saudi coalition immediately until an investigation of the alleged crimes is complete. If Obama were to do that, he could effectively end the mass slaughter within hours.

Lieu and other Democrats have notably refrained from directly blaming Obama for the violence, saving their harshest wards for a politically easier target: the Saudis.

“Either the Saudi coalition is intentionally targeting civilians or they are not distinguishing between civilians and military targets,” Lieu wrote. “Both would be war crimes.”

The Obama administration is currently conducting a review of its support for the Saudi-led coalition, prompted by Saturday’s attack.

But that investigation does not mean the U.S. will immediately stop aiding the Saudis and their partners, including the United Arab Emirates, Jordan, Morocco and others. And the Obama administration’s decision to directly hit the Houthi rebels for the first time on Thursday — in response to multiple attempted attacks on U.S. ships — suggests that the U.S. is only becoming more deeply embroiled in Yemen’s war.

The U.S. will respond again if the Iran-backed rebels try another assault, White House spokesman Eric Schultz told reporters Thursday afternoon.