Given the military stalemate on the ground in Yemen, it may be that the next meaningful battle in that war is about to be fought on the floor of the U.S. Senate.

Perhaps as early as Tuesday, March 20, just about the time Saudi Crown Prince Mohammed bin Salman will be meeting with senior administration officials in Washington, the Senate may vote on S.J.Res.54, which calls for “the removal of U.S. armed forces from hostilities in the Republic of Yemen that have not been authorized by Congress.” Those forces have been deployed in support of a military coalition led by Saudi Arabia that seeks to restore the internationally recognized government of exiled Yemeni President Abd Rabbu Mansour Hadi.

The motivation, according to the resolution’s principal sponsors – Sens. Mike Lee (R-UT), Bernie Sanders (I-VT), and Chris Murphy (D-CT) – is twofold: first, to restore to Congress the sole authority it enjoys under the U.S. Constitution to declare war. For years, members of Congress have claimed that its authority has been usurped by a series of U.S. presidents who have sent U.S. forces into hostilities abroad without consultation with the legislative branch. The other stated reason is to provide relief to the civilian population of Yemen, which has endured three years of protracted airstrikes by Saudi Arabia and its allies, a campaign that has contributed materially to the humanitarian disaster that now grips the country. March 25 marks the third anniversary of the Saudi-led coalition’s entrance into what had been up to that point a civil war in Yemen, which was sparked by the seizure of the capital, Sanaa, in September 2014 by Ansar Allah, the armed militia associated with the Houthis, a rebellious Zaydi Shia movement that hails from the north of the country.

The Senate resolution invokes the War Powers Resolution of 1973 as the basis for its claim that U.S. forces “have been introduced into hostilities” by virtue of the fact that they provide to the Saudi coalition targeting assistance, intelligence sharing, and aerial refueling of Saudi fighter jets that have been conducting the airstrikes over Yemen.

The Defense Department disputes the claim. In a March 14 letter to Senate Majority Leader Mitch McConnell, Defense Secretary Jim Mattis asserted that neither President Barack Obama nor President Donald J. Trump authorized the use of U.S. military force against the Houthis, who still control most of Yemen’s heavily populated highlands and the principal Red Sea port, Hodeidah. Mattis characterized the assistance the United States provides to the Saudi-led coalition as “non-combat support.”

Notably, the resolution only addresses the support provided by U.S. forces battling the Houthi insurgency, and specifically excludes the small contingent of U.S. special operations forces conducting counterterrorism operations with counterparts from the United Arab Emirates and locally recruited militias against fighters associated with Al-Qaeda in the Arabian Peninsula and the Islamic State in Iraq and the Levant. The deployment of these forces comes under the Authorization of the Use of Military Force, which in the immediate aftermath of the September 11, 2001 attacks granted the president the authority to commit U.S. forces to military operations against any organization with links to al-Qaeda.

In the lead-up to the expected floor vote, the resolution’s sponsors have been working assiduously to win the support of senators from both parties in sufficient number to ensure its passage. While the bill enjoys broad Democratic support, Republicans have been lukewarm, at best. In fact, the bill may be derailed by Republican leadership, which has signaled an interest in tabling the legislation for consideration by the Senate Foreign Relations Committee before bringing it before the full Senate, which would effectively prevent the vote from taking place.

In contrast, the bill’s prospects for passage in the House of Representatives – should it ever make it out of the Senate – are said to be stronger. In November 2017, members of the House voted overwhelmingly in favor of a very similar resolution, albeit one that had morphed into a nonbinding resolution as part of negotiations that allowed sponsors to bring it to the floor. In that instance, the resolution passed by a vote of 366 to 30.

The coincidence of the vote on the Senate resolution likely taking place just as the visit to the United States of Saudi Crown Prince Mohammed bin Salman gets underway is a function of the legislative calendar more than any design of the bill’s sponsors. Nevertheless, the timing offers the White House an important talking point for the conversation that will almost certainly take place on Yemen. It allows the administration to point to the impediment an increasingly recalcitrant Congress poses to an open-ended U.S. commitment to the Saudi-led coalition’s war. Perhaps the prospect of steadily diminishing U.S. support will spur Saudi leadership – including the crown prince, the architect of the kingdom’s military intervention in Yemen – to begin to investigate means other than military to resolve the conflict.

In fact, reports surfaced last week that senior Saudi officials have been engaging in quiet discussions with chief Houthi negotiator Mohammed Abdel-Salam in the Omani capital, Muscat. Adel-Salam traveled to Muscat in late January accompanying a U.S. citizen who had been held by the Houthis, and stayed on, making known his availability for discussions about a resumption of talks regarding a political settlement to the war. These recent talks, which reportedly are between the Houthis and the Saudis, without participation by the Hadi government, have not been confirmed by the coalition itself. If they are taking place, it may signal that Riyadh is already sensing that international patience with its war effort is running thin and it needs to be seen as actively pursuing a political solution.

It is too early to tell if momentum in Washington to bring the war to a negotiated settlement will be sustained. However, in addition to recent congressional action, the White House in December 2017 expressed concern about the delivery of humanitarian assistance to Yemen’s civilian population, and called directly on the Saudis to “completely allow food, fuel, water, and medicine to reach the Yemeni people who desperately need it.” If such pressure were to continue, and be echoed in other world capitals, it might represent a decisive shift in international public opinion, allowing the faint hope that this month’s third anniversary of the Saudi entrance into Yemen’s war will be the last.