Key Democratic leaders in Congress are pressing Saudi Arabia and the United Arab Emirates to drop their demands for Yemen’s Houthi rebels to unilaterally surrender the key Red Sea port of Hodeidah.

In a letter to the countries’ ambassadors in Washington, five members of the House Democratic leadership raise concerns about the humanitarian toll in the war-plagued country. The letter marks the latest blow to a Gulf coalition that has continued to hemorrhage support in Congress, which has the power to block arms sales and refueling support to the Saudi-led Arab coalition fighting the Iran-backed Houthis.

“We urge you to be flexible with regard to your requirements to avert escalation at [Hodeidah] — specifically your demands that the Houthis unconditionally leave the city and port, and more recently the entire Red Sea coast, immediately,” the lawmakers wrote to Emirati Ambassador Yousef al-Otaiba and Saudi Ambassador Khalid bin Salman Abdul-Aziz Al Saud.

As part of United Nations envoy Martin Griffiths’ efforts to forestall a bloody offensive, the Houthis have offered to turn over management of the port to the UN. The Saudis and Emiratis, however, are demanding a full withdrawal from the area. Democratic leaders also expressed concern that even if the coalition were to retake Hodeidah, the war would continue as the Houthis double down.