WASHINGTON — A war powers resolution to end U.S. military involvement in Yemen’s civil war has more than 50 sponsors, including some Democratic big guns.

The legislation formally introduced Wednesday sets up a showdown on the House floor after the midterms in November, when the House returns from a long recess. Under the War Powers Act, the resolution would be “privileged,” which lets lawmakers force a vote on it.

The lead sponsor, Rep. Ro Khanna, D-Calif., and House Armed Services Committee ranking member Adam Smith, D-Wash., announced their intention earlier this month to introduce the measure. Khanna offered a similar resolution a year earlier, but it was scuttled in a deal that led to a successful nonbinding resolution on the matter.

“One year later, the bloodshed continues with widespread destruction and disease contributing to the world’s worst humanitarian crisis. U.S.-fueled planes continue to drop U.S.-made bombs on innocent victims,” Khanna said in a statement. “This time around, our coalition to end the war has expanded and the call for withdrawing U.S. involvement is louder.”

House Minority Whip Steny Hoyer, D-Md., has since joined with the ranking member of the House Foreign Affairs Committee, Rep. Eliot Engel, D-N.Y. and that of the House Rules Committee, Rep. Jim McGovern, D-Mass.

The three Republican co-sponsors are Reps. Thomas Massie, of Kentucky; Walter Jones, of North Carolina; and Raul Labrador, of Idaho — all outliers in their party on foreign policy matters.

“Congress never authorized military action in Yemen as our Constitution requires, yet we continue to fund and assist Saudi Arabia in this tragic conflict,” Massie said. “It’s long past time Congress held a debate and vote as to whether U.S. soldiers and personnel should be involved in this war.”

The U.S. military supports the Saudi-led coalition fighting Iran-backed Houthi rebels in the 3-year-old civil war. The aid includes arms sales and aerial refueling of coalition fighter jets, which carry out airstrikes in Yemen.

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The United Nations in April called the Yemen conflict the world’s worst humanitarian crisis, and has said the Saudi-led coalition was responsible for most of the 16,700 civilians killed or injured in Yemen over the last three years.

Defense Secretary Jim Mattis has defended U.S. involvement, saying allies have been receptive to U.S. training and advice aimed at avoiding casualties. Other defenders have said the U.S. must participate in the effort as a means of containing Iran.

President Donald Trump, in a speech at the United Nations General Assembly on Tuesday, highlighted the positive work of Arab allies in the conflict.

“The UAE, Saudi Arabia and Qatar have pledged billions of dollars to aid the people of Syria and Yemen, and they are pursuing multiple avenues to ending Yemen’s horrible, horrific civil war,” Trump said.

Secretary of State Mike Pompeo last week allowed the aid to continue by certifying Saudi Arabia and the United Arab Emirates were "undertaking demonstrable actions to reduce the risk of harm to civilians” and taking steps to end the war.

A Wall Street Journal report said that decision involved $2 billion worth of pending weapons sales to Gulf allies — an allegation that has further inflamed lawmakers and humanitarian groups in opposition to U.S. involvement.

On Wednesday, Engel said the certification isn’t credible in light of recent civilian casualties, but said he was not minimizing the threats to Saudi Arabia and the United Arab Emirates.

“Iranian assistance has upgraded Houthi weaponry, and I remain committed to helping our allies mitigate this threat. I also recognize that their cooperation is critical to the fight against ISIS-Y [the Islamic State group in Yemen] and al-Qaida in the Arabian Peninsula,” he said.