US Secretary of State Mike Pompeo stressed on Wednesday that Saudi Arabia and the United Arab Emirates are acting to reduce risks to civilians in their military operations in Yemen. The assessment is required by Congress for it to continue allowing US air tankers to refuel Saudi and UAE warplanes. In his certification, 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." 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. Pompeo said Washington would work closely with the coalition 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.