As Congress and the administration look for ways to contain Iran, one Democratic senator is launching a new effort to deny weapons to Tehran’s chief rival in the Middle East: Saudi Arabia.

The Senate hasn’t taken a vote to prevent arms sales to longtime U.S. ally Saudi Arabia for three decades. But Murphy’s efforts comes amid grumbling from lawmakers that the country, despite being a key U.S. ally in the region and one of the world’s biggest purchasers of U.S.-made munitions, isn’t necessarily acting in the national security interests of the United States.

The frustrations echo all the way up to the White House, where Obama has expressed frustrations about Saudi Arabia’s conduct in the Middle East, and recently described the U.S.-Saudi relationship to The Atlantic as “complicated.”

But by his own admission, Murphy is unlikely to rally much support from the administration or his peers. Lawmakers and administration officials may openly criticize Saudi Arabia – but they also count the powerful, oil-rich nation as a key ally in the Middle East, especially when it comes to counterbalancing Iran and routing the Islamic State from its strongholds.

“I don’t think that the result of the Iran nuclear agreement should be the United States doubling down on proxy wars in the Middle East that are contrary to our national security interests,” Murphy said in an interview.

He complained that recent Saudi military campaigns backed by the U.S. and fueled by U.S.-made weapons have “hurt the U.S. and has strengthened the terrorist groups that we’re fighting.”

Chief among Murphy’s complaints is Saudi Arabia’s conduct in neighboring Yemen, where a Saudi-backed coalition has been fighting Iranian-backed rebels. The conflict, which just entered a tenuous ceasefire on Monday, has been on the back-burner for U.S. policymakers who are more acutely focused on containing Iran and fighting the Islamic State – a battle in which they’d like to see Saudi Arabia play a bigger part.

Saudi Arabian forces once participated in the U.S.-coalition fight against ISIS by carrying out airstrikes against Syria, but pulled back over the last year as Riyadh shifted its military focus toward Yemen. But as the fighting there intensified, al-Qaeda gained a stronger foothold and human rights groups complained that Saudi Arabia’s involvement was causing the civilian death toll to mount. They called on the United States to stop selling arms to its ally.

Murphy wants to subject sale of air-to-ground weapons and ammunition – the bulk of what the U.S. sells to Saudi Arabia – to a certification process, in which the White House would have to guarantee the Saudis are really targeting terrorists and not civilians in Yemen. He would like to ensure that the Saudis are playing a greater role in providing humanitarian aid and protection in conflicts throughout the Middle East, and are contributing effectively to U.S. national security priorities in the region – particularly the fight against ISIS.

“In Yemen today we are blamed for the slaughter and the civilian casualties as much or more than the Saudis,” Murphy said, adding that the Yemen conflict was “becoming recruiting fodder for jihadist organizers.”

But  pulling arms out of the hands of allies is not something Congress does often or hastily.

A recent effort from Sen. Rand Paul (R-Ky.) to stop the sale of F-16s to Pakistan was met with bipartisan backlash, with lawmakers arguing that while Pakistan wasn’t doing a perfect job of fighting extremism, yanking weapons out of their hands would only make the problem worse and jeopardize the alliance. In the end, only 24 lawmakers – 12 Republicans and 12 Democrats – voted in favor of Paul’s measure.

Paul is currently the only co-sponsor of Murphy’s resolution. But Murphy’s attempt to put conditions on selling arms to Saudi Arabia is likely an even more uphill slog, considering the U.S.’s priorities in the Middle East, the history of the U.S.-Saudi alliance, and the billions of dollars that Saudi contracts are worth to U.S. arms manufacturers.

“Criticism of Saudi Arabia has been counter-cultural in this town for a long time, so I’m introducing this resolution with eyes wide open,” Murphy said. But, he added, “Saudi Arabia has gotten off the hook for a very long time when it comes to the flow of money out of Saudi Arabia into the hands of radical religious organizations…if we’re serious of eliminating the flows for extremist activities we’ve got to press the Saudis harder.”