US President Donald Trump on Friday approved sending American troops to bolster Saudi Arabia’s air and missile defenses after the largest-ever attack on the kingdom’s oil facilities, which Washington has squarely blamed on Iran.

The Pentagon said the deployment would involve a moderate number of troops - not numbering thousands - and would be primarily defensive in nature. It also detailed plans to expedite delivery of military equipment to both Saudi Arabia and the United Arab Emirates.

Reuters has previously reported that the Pentagon was considering sending anti-missile batteries, drones and more fighter jets. The United States is also considering keeping an aircraft carrier in the region indefinitely.

“In response to the kingdom’s request, the president has approved the deployment of US forces, which will be defensive in nature and primarily focused on air and missile defense,” US Defense Secretary Mark Esper said at a news briefing.

“We will also work to accelerate the delivery of military equipment to the kingdom of Saudi Arabia and the UAE to enhance their ability to defend themselves.”

The Pentagon’s late Friday announcement appeared to close the door to any imminent decision to wage retaliatory strikes against Iran following the attack, which rattled global markets and exposed major gaps in Saudi Arabia’s air defenses.

Trump said earlier on Friday that he believed his military restraint so far showed “strength,” as he instead imposed another round of economic sanctions on Tehran.

But the deployment could further aggravate Iran, which has responded to previous US troop deployments this year with apprehension. It denies responsibility for the attack on Saudi Arabia.

Yemen’s Iran-aligned Houthi movement, which has been battling a Saudi-led military coalition that includes the UAE, has claimed responsibility for the strikes.