The House has backed a bill to block implementation of the Iran nuclear deal until Tehran pays some $43 billion in damages that U.S. courts have awarded to victims of Iranian-sponsored terror.

The bill passed on a 251-173 vote on Thursday, but is unlikely to clear the Senate or become law.

President Barack Obama has threatened to veto it, saying it undermines the international accord that provides Iran billions in sanctions relief in exchange for constraints on its nuclear program.

The bill, by Pennsylvania Republican Rep. Patrick Meehan, would prohibit the president from lifting sanctions until the victims' claims are paid.

Meehan says opponents put "Iran's terror machine" before American victims of Iranian terror.

Democrats say the GOP is using the bill to stop implementation of the deal.