The House passed a bill today that could inhibit the sale of commercial aircraft to Iran, potentially running afoul of the landmark 2015 nuclear accord.

A total of 23 Democrats joined their Republican counterparts to pass the bill from Rep. Roger Williams, R-Texas, 252-167. But the bill’s future is unclear in the Senate, where final passage would be contingent on the support of Democrats who have resisted Republican efforts to alter or withdraw from the Joint Comprehensive Plan of Action (JCPOA).

Republicans need the support of at least eight Democrats to get the bill through the Senate’s 60-vote threshold. They’ve already lost a key supporter in Sen. Ben Cardin, D-Md., the top Democrat on the Foreign Relations Committee.

“Sen. Cardin is not supportive of legislation that would violate the United States’ obligations under the JCPOA, which this bill would appear to do since the civilian aircraft issue was specifically called for in the agreement,” Sean Bartlett, a spokesman for Cardin, told Al-Monitor. “Though he opposed the original agreement, since it was entered into he has repeatedly called for rigorous US oversight and compliance.”