Two US Senators introduced legislation on Wednesday that would halt future sales of aerial munitions to Saudi Arabia until President Obama verifies that the Saudi government is respecting international humanitarian law in waging war in Yemen, that it doesn't support listed terrorist groups, and that it is pursuing all measures to eradicate al-Qaeda and the Islamic State group.

Senators Chris Murphy (D-CT) and Rand Paul (R-KY) said that in light of the civilian toll of the US-backed Saudi-led intervention in Yemen, the White House must ensure that American weapons are not being used in attacks on innocents. Both said that it was unclear if the Saudi-led coalition's operations in Yemen, which the US government immediately supported a year ago, advance US interests in the Middle East.

"The more it drags on, the clearer it becomes that our military involvement on behalf of the Saudi-led coalition is prolonging human suffering in Yemen and aiding the very groups that are intent on attacking us," said Murphy.

According to Congressional researchers, the US has sold more than $100 billion in arms to Saudi Arabia since 2010. Those sales have continued during the increasingly bloody war in Yemen. Saudi coalition airstrikes, which groups like Human Rights Watch and Amnesty International have explicitly tied to US arms, have caused the majority of more than 3,200 civilian deaths since last March, according to the United Nations.

In November, the US announced a $1.3 billion deal that would in part replenish bomb stockpiles spent during the air campaign in Yemen. The Senate bill would apply specifically to all sales of air-to-ground munitions to Saudi Arabia.

"For too long, the Obama administration has not been holding countries receiving US military munitions accountable in the Middle East," said Paul. "It is no secret that Saudi Arabia's record on strictly targeting combatants and legitimate military targets in Yemen has been questionable."

Under US law, the State Department must notify of Congress of any arms sale to a foreign government, and legislators must approve the sale. In practice, the process is merely procedural, especially for countries regarded as stalwart allies in Washington, such as Saudi Arabia. The text introduced by Murphy and Paul on Wednesday would add an extra layer of vetting, requiring the president to attest that Saudi Arabia is not supporting or providing "lethal" aid to any group designated as a terrorist organization by the US, that Riyadh and its coalition partners "are taking all feasible precautions to reduce the risk of harm to civilians," and that they are complying with international humanitarian law.

Additionally, the president will have to determine if Saudi Arabia is facilitating the flow of humanitarian aid into Yemen and is "taking all necessary measures" to target terror groups including al-Qaeda and the Islamic State "as part of its military operations in Yemen."

The year-long Saudi intervention in Yemen has coincided with a vast territorial expansion by al-Qaeda's local branch, known as al-Qaeda in the Arabian Peninsula (AQAP). Murphy previously raised questions about the spread of AQAP in Yemen, a development that conveys a failure of Washington's stated military goals in the region. Though the Saudi-led coalition has pummeled civilian sites in areas controlled by Houthi rebels and their allies, it has rarely gone after AQAP.

The bill notes that a UN panel of experts in January found that the coalition had repeatedly targeted civilians and civilian objects, thereby violating international humanitarian law. Among the sites listed by the panel were camps for the internally displaced, weddings, residential areas, medical facilities, schools, mosques, and markets, as well as civilian infrastructure such as ports and highways.

The UN has called for an independent international investigation into crimes committed in Yemen, but last fall Saudi Arabia defeated an effort at the Human Rights Council in Genevato establish one. An investigatory body nominally created by the Riyadh-supported Yemeni government of President Abd Rabbuh Mansur Hadi, as well as a domestic Saudi mechanism — both widely viewed as intrinsically biased — have yet to show results.

American authorities, meanwhile, have not launched any official review of their support package for the Saudi coalition.

In addition to billions in arms sales, the US has placed a 45-member planning cell inside Saudi Arabia and provides the coalition with daily refueling sorties, intelligence sharing, and logistical assistance. Experts say that without Washington's support package, Saudi Arabia would have difficulty perpetrating its intervention in Yemen.

The bill's introduction comes two days after the start of a brokered cessation of hostilities in the country, ahead of planned peace talks in Kuwait next Monday. The fate of those negotiations are unclear, and several previous ceasefires have disintegrated.

VICE News asked the Pentagon and US Central Command on Tuesday if their assistance program for the Saudi coalition had changed in any way in light of the start of the cessation, but did not receive a reply by Wednesday afternoon.

Even if the Saudi-led air war in Yemen were to continue with similar intensity and civilian bloodshed, winning approval of the resolution is expected to be an uphill battle in Washington. If it does gain wider traction among legislators, the arms industry will likely lobby heavily against a deal that could potentially destabilize a hugely profitable weapons trade with Gulf countries.