US Secretary of State Mike Pompeo said on Wednesday he has "certified" that coalition partners Saudi Arabia and the United Arab Emirates are acting to reduce risks to civilians in their military operations in Yemen.
The assessment, which is required by Congress for it to continue allowing US air tankers to refuel Saudi and UAE warplanes, comes after a string of high-profile coalition strikes that have killed scores of civilians, many of them children.
In a statement, Pompeo noted that both countries "are undertaking demonstrable actions to reduce the risk of harm to civilians and civilian infrastructure resulting from military operations of these governments."
He did not provide additional details, but on September 1, the coalition admitted that "mistakes" had been made in an August air strike that killed 40 children.
The bombing on a crowded market in part of northern Yemen held by Houthi rebels killed a total of 51 people, according to the Red Cross.
The Yemen conflict has triggered the world's worst humanitarian crisis, with the UN estimating that as many as 10,000 people have died, most of them civilians, since the coalition launched military operations in 2015.
Twin strikes south of the rebel-held Red Sea port of Hodeida on August 23 killed 26 children, the UN has said.
The US has drawn sharp criticism for its ongoing support to the coalition, which also includes intelligence sharing and targeting information.
Aid groups slammed Pompeo's certification, saying it would ensure further civilian bloodshed.
"With Secretary Pompeo's certification, the State Department demonstrated that it is blindly supporting military operations in Yemen without any allegiance to facts, moral code or humanitarian law," Oxfam America said in a statement.
Brookings Institution fellow Scott Anderson said Congress must push for more information on the basis of the certification, and challenge Pompeo if this is deemed inadequate.
Democratic Congressman Ro Khanna called the certification a "farce."
"The Saudis deliberately bombed a bus full of children. There is only one moral answer, and that is to end our support for their intervention in Yemen," Khanna said on Twitter.
The coalition supports the internationally recognised government of President Abedrabbo Mansour Hadi, which is fighting Iran-backed Houthi rebels who seized control of Sanaa in 2014.
US Defense Secretary Jim Mattis issued a separate statement endorsing the certification, saying the UAE and Saudis are making "every effort" to reduce the risk of civilian casualties and collateral damage.
Mattis last month warned that US support for the coalition was "not unconditional," noting that the coalition must do "everything humanly possible to avoid any innocent loss of life, and they support the UN-brokered peace process."
Pompeo said Washington would work closely with the coalition to ensure Saudi and UAE support for UN peace efforts and to allow unimpeded access for commercial and humanitarian relief supplies to reach Yemenis.
"The Trump administration has been clear that ending the conflict in Yemen is a national security priority," Pompeo said.
Long-awaited, UN-brokered peace talks between the Saudi-backed government and the Houthi rebels failed to take place as planned last week in Geneva.
The Houthis said the UN had failed to guarantee the safe return of their delegation from Geneva to Sanaa and to secure the evacuation of wounded rebels to Oman.