Defense Secretary Jim Mattis has asked the White House to lift Obama-era restrictions on U.S. military support for Persian Gulf states engaged in a protracted civil war against Iranian-backed Houthi rebels in Yemen, according to senior Trump administration officials.

In a memo this month to national security adviser H.R. McMaster, Mattis said that “limited support” for Yemen operations being conducted by Saudi Arabia and the United Arab Emirates — including a planned Emirati offensive to retake a key Red Sea port — would help combat a “common threat.”

Approval of the request would mark a significant policy shift. U.S. military activity in Yemen until now has been confined mainly to counterterrorism operations against al-Qaeda’s affiliate there, with limited indirect backing for Gulf state efforts in a two-year-old war that has yielded significant civilian casualties.

It would also be a clear signal of the administration’s intention to move more aggressively against Iran.