Anti-war advocates are launching an 11th-hour bid to stop U.S. Congress from approving a $1.15 billion arms sale to Saudi Arabia in its fight against Houthi rebels in Yemen, which was announced earlier this month.

Chief among them are the activist group CODEPINK and U.S. Rep. Ted Lieu (D-Calif.), who are calling on Congress to block the sale at least long enough to give lawmakers time to "give these issues the full deliberation that they deserve."

Congress has 30 days to object to the deal, announced August 9. Lieu has bipartisan support in the House of Representatives from Reps. John Conyers (D-Mich.), Ted Yoho (R-Fla.), and Mick Mulvaney (R-S.C.), all of whom are sending a letter to the Obama administration on Thursday asking to delay the trade, citing the recent bombings of hospitals, schools, and residential areas by the Saudi-led coalition in Yemen.

"I taught the law of war when I was on active duty," Lieu told The Intercept on Monday. (Lieu served in the U.S. Air Force and is an Air Force Reserves colonel.) "You can't kill children, newlyweds, doctors and patients—those are exempt targets under the law of war, and the coalition has been repeatedly striking civilians. So it is very disturbing to me. It is even worse that the U.S. is aiding this coalition."

Outside of Capitol Hill, CODEPINK and other groups, including RootsAction.org and the Yemen Peace Project, are circulating a petition calling on representatives to sign onto Lieu's letter.

"[J]ust in the last several days, a Saudi airstrike on a school in Yemen killed 10 children, and a Saudi airstrike on [a Doctors Without Borders/Médecins Sans Frontières (MSF)] hospital in Yemen killed 11 people," the petition states. "Amnesty International has documented airstrikes by the Saudi Arabia-led coalition across Yemen that appear to have deliberately targeted civilians and civilian facilities, such as hospitals, schools, markets, and places of worship."

The bombings became so indiscriminate, and the reassurances from the coalition so vague, that MSF last week was forced to pull its staff from the hospitals the medical charity supports in Yemen's northern Sana'a and Hajjib provinces.

"MSF asks the Saudi-led coalition and the governments supporting the coalition, particularly the U.S., U.K., and France, to ensure an immediate application of measures to substantially increase the protection of civilians," MSF general director Joan Tubau said at the time.

But the arms deal is going in the opposite direction, the advocates said. CODEPINK warned that "Continued U.S. arms sales to Saudi Arabia could make the U.S. complicit in potential war crimes committed by the Saudi-led coalition."

Moreover, the deal was announced while Congress was in recess, giving them little time to debate it before the 30-day window closes, the group noted. Lawmakers return to session on September 5.

Lawmakers in the Senate are also gearing up to block the sale. One of them is Sen. Rand Paul (R-Ky.), who told Foreign Policy earlier this month that he would "work with a bipartisan coalition to explore forcing a vote on blocking this sale. Saudi Arabia is an unreliable ally with a poor human rights record. We should not rush to sell them advanced arms and promote an arms race in the Middle East."

Paul is joined by Sen. Chris Murphy (D-Conn.), who in June warned that "Every single civilian death inside Yemen is attributable to the United States."

"If you talk to Yemeni Americans, they will tell you in Yemen this isn't a Saudi bombing campaign, it's a U.S. bombing campaign," he said.