The veto — the second in Trump's presidency — was expected, and Congress lacks the votes to override it. But passing the never-before-used war powers resolution was viewed as a milestone for lawmakers.
The truce has largely held but the withdrawal has yet to materialise amid deep mistrust between the Iran-aligned Houthi movement, which controls Hodeidah, and the Saudi-led coalition trying to restore the ousted government of Abd-Rabbu Mansour Hadi.
The UAE has trained and armed thousands of Yemeni fighters, mostly in southern provinces and western coastal areas, as part of the forces battling the Houthis, who control most urban areas including the capital Sanaa and the main port of Hodeidah.
The conflict in Yemen began with the 2014 takeover of Sanaa by the Iranian-backed Houthis, who toppled the government of Abed Rabbo Mansour Hadi. A Saudi-led coalition allied with Yemen's internationally recognized government has been fighting the Houthis since 2015.
The draft resolution, seen by Reuters, authorizes UN Secretary-General Antonio Guterres to deploy - for an initial 30 days - an advance team to begin monitoring and to support and facilitate the deal between the warring parties.
As outrage over the murder of Saudi dissident Jamal Khashoggi in Istanbul by Saudi operatives fused with concern about Yemen, a wave of disquiet swept Washington amid accusations that the US military could be complicit in war crimes.
The US official's reassurances of continued support comes as Sweden hosts the first UN-led peace talks in two years between the warring parties and as Gulf Arab leaders hold an annual summit in Riyadh on Sunday, expected to discuss the war.
Many Yemenis who have fled their homes and farms in and around Hodeidah to head north to the Houthi-held capital Sanaa or to safer areas along the western coast and the southern port city of Aden said that they are struggling to survive.