U.S. media report say President Donald Trump said on Sunday the United States was “locked and loaded” for a potential response to the attack on Saudi Arabia’s oil facilities, after a senior U.S. administration official said Iran was to blame.

U.S. Secretary of State Mike Pompeo on Saturday accused Iran of leading attacks on Saudi oil plants that cut the kingdom’s output roughly in half, ruling out Yemeni involvement and denouncing Tehran for false diplomacy, according to Reuters.

Yemen’s Houthi group claimed credit for Saturday’s attacks on two oil plants at the heart of Saudi Arabia’s oil industry, including the world’s biggest petroleum processing facility.

Pompeo, however, said on Twitter that there was no evidence the attacks came from Yemen.

The U.S. State Department reportedly declined to provide any evidence to bolster Pompeo’s claim.

United Nations investigators have written that the Houthis have acquired advanced drones that could have a range of up to 930 miles.  That leaves open the possibility that the drones used Saturday had flown from Houthi-controlled territory in Yemen.  But they may also have been launched from another country, such as Iraq, or from inside Saudi Arabia itself, says The New York Times.

According to Iranian media reports, Iranian Foreign Ministry spokesman Abbas Mousavi dismissed the U.S. allegations that it was responsible was “pointless”.  A senior Revolutionary Guards commander warned the Islamic Republic was ready for “full-fledged” war.