President Donald Trump spoke by phone with Yemeni President Rashad al-Alimi on Sunday, four people familiar with the matter said, discussing the advances of the Iran-backed Houthis around a vital global waterway.

Alimi requested US support for his Saudi-backed government in its fight against the Houthis, who this month took key areas along the Bab al-Mandeb strait in a lightning offensive.

Two of the sources, one Yemeni and one Western, said Trump had made no direct pledge of military support during the call.

The White House and Yemen’s information minister did not immediately respond to requests for comment.

Trump has said publicly that the US is in contact with the Houthis and that the group has said it will not target U.S. shipping. The US has designated the Houthis as a terrorist organization.

Trump has also rebuffed Saudi requests for military support against the Houthis, Reuters has previously reported.

(Reporting by Timour Azhari in Riyadh; Editing by Toby Chopra)