WASHINGTON, D.C. (NEXSTAR) — As tensions between Iran and the U.S. rise, Senate Democrats are making a last-minute push to prevent an armed conflict.

In the dark, early hours of Friday morning, Senators scrambled to get in one last vote before heading home for recess.

Starting at 5 a.m., one-by-one, Senators trickled into the chamber to vote on a measure that Virginia Democratic Senator Tim Kaine says could stop an all-out war from breaking out at any moment with Iran.

Kaine says his measure with New Mexico Democrat Tom Udall would specifically prohibit President Trump from using military action against Iran without approval from Congress.

But the Republican-controlled Senate rejected the measure.

Majority Leader Mitch McConnell says because tensions with Iran are rising, the U.S. should be able to respond at a moment’s notice.

“This is a terrible idea at any moment,” said McConnell. “Let alone as Iran is escalating its violence and searching for any sign of American weakness.”

Earlier this week, President Trump slapped new sanctions on Iran in retaliation for shooting down a U.S. drone — he’d originally considered a military strike, but called it off minutes before it was scheduled to launch.

House Democrats say they plan to introduce a similar measure in the House when Congress returns next month.