Secretary of State Mike Pompeo has certified that Saudi Arabia and the UAE are working to reduce civilian casualties as a humanitarian crisis unfolds in Yemen.

The fiscal 2019 National Defense Authorization Act had given Pompeo 30 days to make the certification amid mounting civilian casualties in Yemen. The Trump administration is facing pressure from critics over the U.S. military's role in refueling Saudi Arabian and the UAE jets and other military support as the two Middle Eastern countries battle Houthi rebels in Yemen. In August, a Saudi jet dropped a bomb on a school bus in Yemen, killing dozens of children.

"Ending the conflict in #Yemen is a national security priority," Pompeo tweeted. "The United States will continue to work with the Saudi-led Coalition to maintain support for UN Special Envoy Martin Griffiths and the UN-led effort to facilitate a comprehensive political agreement."

Defense Secretary Jim Mattis backed Pompeo's declaration.

"I endorse and fully support Secretary Pompeo's certification to the Congress that the governments of Saudi Arabia and United Arab Emirates are making every effort to reduce the risk of civilian casualties and collateral damage to civilian infrastructure resulting from their military operations to end the civil war in Yemen," Mattis said. "The Saudi-led coalition's commitment is reflected in their support for these UN-led efforts."

Sens. Todd Young and Jeanne Shaheen had warned that lawmakers could turn against the administration's activities in Yemen if Pompeo had not complied with the deadline to certify.

“For the sake of the United States’ interests and our humanitarian principles, we hope the administration complies with the law and submits a good-faith certification by Wednesday," they wrote in the Washington Post. "If that does not happen, support for the coalition in Congress may reach a breaking point as the world’s worst humanitarian crisis deteriorates further."