President Donald Trump on Sunday night said the United States is “locked and loaded” and ready to intervene with whoever is behind the drone attacks on Saudi Arabia’s oil supply.

“Saudi Arabia oil supply was attacked,” the president said in a series of tweets.

“There is reason to believe that we know the culprit, are locked and loaded depending on verification, but are waiting to hear from the Kingdom as to who they believe was the cause of this attack, and under what terms we would proceed!”

Early on Saturday, two major Saudi Arabian oil facilities were set ablaze in a coordinated drone attack, forcing the kingdom to shut down half its oil production and sparking fears of a big jump in oil prices.

Leaders of the Iranian-backed Houthi rebel group claimed responsibility for the attack on the Abqaiq refinery, saying they launched drones from 500 miles away in Yemen.

Secretary of State Mike Pompeo dismissed the Houthis’ claim and blamed Iran for the strike, tweeting Saturday, “There is no evidence the attacks came from Yemen.”

Iran on Sunday denied the US claims that it was behind the drone attacks on the largest oil refinery in the world and threatened to retaliate on American forces abroad if the United States takes military action.