On Friday, the Washington Post reported that the Trump administration would end mid-air refueling support to the Saudi- and United Arab Emirates-led coalition that has been bombing Yemen, cutting off what is widely seen as the most significant pillar of American support for the brutal campaign.

But progressives in Congress are pushing for more, aiming to cut off weapons sales and pass a measure in both chambers that would force the withdrawal of U.S. forces from Yemen. The measure — which was introduced by Rep. Ro Khanna, D-Calif., in the House and by Sens. Chris Murphy, D-Conn.; Bernie Sanders, I-Vt.; and Mike Lee, R-Utah, in the Senate — relies on the legal theory that intelligence and logistical support amount to “hostilities” under the 1973 War Powers Act, and therefore must be authorized by Congress, which has not approved U.S. involvement in the war between the coalition and a rebel group known as the Houthis in Yemen.

In a phone interview on Friday, Khanna told The Intercept that he was “cautiously optimistic” about the news, but wants to pass the measure to ensure that the Trump administration follows through on its decision.

“This is a major change. It could avert a humanitarian crisis,” Khanna said. “From everything that I’ve understood — from activists on the ground, from people who are briefed on policy — the war could not continue without the assistance of U.S. refueling.”

It is not clear whether that is the case, however. Citing anonymous sources, the Post reported that the administration’s decision “was prompted at least in part by the Saudi military’s increased aerial refueling capacity,” suggesting that the withdrawal of U.S. support may not have as much impact as Khanna and others hope.

“I do think that Congress should memorialize it by passing Senate Resolution 54 and House Resolution 138,” Khanna said, referring to the measures by their respective bill numbers. “Similar to what we did in Somalia’s case, when the White House said that we weren’t going to have any intervention, Congress went ahead and passed both of the War Powers Resolution [measures], just to make sure that was definitive.”

Sanders, too, said he would press for the resolution’s passage. “I’m glad that the Trump administration is ending U.S. refueling of Saudi aircraft in Yemen’s devastating war. … U.S. participation in this conflict is unauthorized and unconstitutional and must end completely,” he said in a statement Friday evening. “I will soon bring Senate Joint Resolution 54 back to the floor for another vote, so the Senate can compel an end to U.S. participation in the Yemen war as a matter of law, not simply as a matter of the president’s discretion.”

Murphy also stressed that the administration should cut off all forms of support, not just refueling. “Why are we still helping the Saudis with targeting? Why are we still selling them the bombs at a discount?” Murphy asked in a statement. “Now that it’s no longer a secret that the war in Yemen is a national security and humanitarian nightmare, we need to get all the way out.”

The U.S. has been assisting Saudi Arabia and the UAE in their intervention since March 2015, after the internationally backed President Abdrabbuh Mansour Hadi was deposed by the Houthis. The U.S. is not directly involved in combat operations against the rebel group — which has received a small amount of support from Iran — but has provided weapons, intelligence, and mid-air refueling for the coalition.