The Senate will push this week to end U.S. military support for the Saudi Arabia-led war in Yemen, potentially cutting off intelligence, materiel and midair pufueling assistance to the Kingdom’s forces, just as Saudi Crown Prince Mohammed bin Salman arrives in Washington for a two-week visit of the United States.

The vote, which may come as early as Tuesday, could deliver an embarrassing rebuke to the 32-year old heir to the throne as he plans to meet President Donald Trump and other members of American political leadership. It comes at a time when the U.S. and Saudi Arabia have been working to restore their relationship, which has deteriorated in recent years due to an array of diplomatic and security-related issues in the Middle East.

Bin Salman, who currently serves as defense minister but is the de facto ruler of the Kingdom, is credited as the architect of the three-year old conflict in Yemen that pits Saudi-backed forces against Iranian-backed Houthi rebels. The war has plunged the Arab world’s poorest nation into a humanitarian crisis that is worsened daily by famine, widespread disease and the deaths of civilians caught in the crossfire.

The United Nations has said that more half of the more than 10,000 people who have been killed are civilians, and the lives of millions are potentially at risk from famine. The grim forecast has intensified calls by human rights groups to halt the violence.

The U.S. government has provided intelligence, munitions and midair refueling to Saudi warplanes since operations kicked off in 2015. But a bipartisan group — Republican Sen. Mike Lee of Utah, Independent Sen. Bernie Sanders of Vermont, Democratic Sen. Chris Murphy of Connecticut and six other co-sponsors — recently introduced a joint resolution to stop the U.S. military from aiding Saudi war efforts in Yemen.

The resolution intends to revitalize the debate over Congress’ constitutional role in declaring war, as military action in Yemen was never voted on. Under the Constitution, only Congress can declare war, but it not formally done so since the 1940s.

“Our military’s involvement in Yemen has not been authorized by Congress as is required by the U.S. Constitution,” Lee said last week on the Senate floor, calling the war “illegal” and “unauthorized.” The vote faces long odds but will at the very least serve as a symbolic admonition to bin Salman, who wants to promote closer ties between Washington and Riyadh.

The Pentagon has asked Congress to reject the resolution, claiming it will jeopardize U.S. military standing in the Middle East and worsen civilian casualties.

Gen. Joseph Votel, head of U.S. Central Command, which oversees military operations in the Middle East, told the Senate Armed Services Committee last week that American support gives the U.S. “access and it gives us influence” over the Saudis.

“From my perspective, it’s better for us to stay engaged with them and continue to influence this,” Votel said on March 13. “They want this type of support, and they want to improve their capabilities.”

Defense Secretary James Mattis sent a letter on Wednesday to Majority Leader Mitch McConnell explaining why it was in the U.S. interest to continue to back Saudi operations.

“Withdrawing U.S. support would embolden Iran to increase its support to the Houthis, enabling further ballistic missile strikes on Saudi Arabia and threatening vital shipping lanes in the Red Sea, thereby raising the risk of a regional conflict,” Mattis wrote.

The U.S. and its allies have determined that the Houthis are proxy forces of Iran, Saudi’s arch rival in the region. For almost 40 years, the two countries have engaged in a contest for power, fighting mostly through proxies. In 2015, armed Houthis quickly swept across Yemen and forced the U.S.-backed president into exile. The Obama Administration initially provided military support to the Saudis and their coalition while simultaneously pursuing the landmark nuclear deal with Iran.

By the end of Obama’s presidency, the U.S. had pulled back most of its support to the Yemen campaign and even stopped some weapon sales due to claims of mounting civilian casualties. The long-standing relationship, built around American’s demand for Saudi oil and the Saudi’s need for American military might, was at one of the lowest points in its more than 70-year history.

However, Trump’s rise to power reignited U.S. military support for the war effort and U.S.-Saudi strategic partnership. He visited Riyadh on his first foreign trip and intensified military collaboration and boosted weapon sales.

The situation in Yemen, meanwhile, became more dire. More than 20 million people, including 11 million children, are in urgent need of humanitarian supplies. Late last year, Saudi Arabia closed the border in retaliation for an intercepted Iranian-made ballistic missile near the capital, Riyadh, allegedly fired by Houthi rebels. The Saudis sealed all entry via land, air, and sea to stem suspected arms smuggling. The blockade has since been lifted.

Bin Salman, in an interview that aired Sunday with CBS, appeared to blame the Houthis for the continued suffering.

“It is truly very painful, and I hope that this militia ceases using the humanitarian situation to their advantage in order to draw sympathy from the international community,” he said. “They block humanitarian aid in order to create famine and a humanitarian crisis.”

The situation in Yemen will be one of the primary topics of discussion when bin Salman meets this week with Trump at the White House, senior administration officials told reporters Monday. The crown prince will also sit down for dinner with Trump’s national security adviser, Lt. Gen. H.R. McMaster, and meet with several Cabinet members, including Mattis and newly named Secretary of State nominee Mike Pompeo.

“We’re working with all sides toward a political settlement that ends the conflict and dire humanitarian situation in Yemen,” said one official, who wasn’t authorized to speak publicly on the matter. “As you know, Yemen is incredibly complex. But our goal is consistent: We want to work with our international partners to ultimately bring peace, prosperity, and security in Yemen.”

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Write to W.J. Hennigan at william.hennigan@time.com.