Sens. Tim Kaine (D-VA) and Rand Paul (R-KY), leading voices in the Senate on war powers issues, introduced a war powers resolution on Friday to block military action against Iran without congressional approval.

The resolution comes after weeks of threats by President Donald Trump against the Iranian regime to intervene on behalf of anti-regime protesters, and amid a U.S. military buildup in the Middle East.

Kaine and Paul can force a vote in the Senate on the resolution, as Kaine has done with resolutions related to a series of other military actions taken by the Trump administration, including last summer’s Operation Midnight Hammer strikes on Iranian nuclear facilities.

The Senate blocked that resolution by a 53-47 vote; Paul voted with most Democrats in favor of the resolution while Sen. John Fetterman (D-PA) voted with most Republicans against it.

Most recently, five Senate Republicans voted with Democrats for a procedural motion on a resolution to block further military action against Venezuela, but two ultimately flipped, under pressure from the Trump administration, on the final vote, blocking its passage.

Republicans were generally supportive of the U.S. strikes on Iran last summer, and some Democrats did praise the action after the fact, even as they expressed concerns about the administration’s unilateral action without congressional approval.

Trump has cited presidential self-defense authorities in carrying out various military actions around the world, including last summer’s strikes in Iran.