President Donald Trump on Saturday offered U.S. support for Saudi Arabia’s self-defense in a phone call hours after drone strikes left swaths of Saudi oil fields aflame and disrupted global energy production.

Two sites, including the world’s largest oil processing facility and a massive Saudi oil field, were hit by explosives, leaving a smoke trail reportedly visible from space.

Trump, the White House confirmed, told Saudi Crown Prince Mohammad Bin Salman that the U.S. “strongly condemns today’s attack on critical energy infrastructure.”

Yemen’s Houthi rebels claimed responsibility for the attack, part of a yearslong war led by the Saudis against the Iran-backed group. Earlier this month a Saudi-led coalition launched airstrikes on a Houthi detention center, leaving at least 100 dead and dozens more injured. It was the Saudi side’s deadliest attack so far this year, according to the Yemen Data Project.

The state-run Saudi Press Agency was first to report the call between American and Saudi leadership.

“Violent actions against civilian areas and infrastructure vital to the global economy only deepen conflict and mistrust,” the White House said in a statement. “The United States Government is monitoring the situation and remains committed to ensuring global oil markets are stable and well supplied.”

Secretary of State Mike Pompeo pinned the Houthi drone strikes directly on Iran, currently at odds with the U.S. as a nuclear arms deal reached by the Obama administration has steadily unraveled in the Trump era.

In a pair of tweets, Pompeo called on the international community “to publicly and unequivocally condemn Iran’s attacks” while hinting at possible consequences for Tehran.