US Secretary of State Michael Pompeo has blamed Iran for attacks on a massive Saudi Aramco oil facility at Abqaiq and the oilfield in Khurais, saying there was no evidence the drones originated in Yemen.

Pompeo tweeted after the White House confirmed that President Donald Trump offered support for Saudi Arabia’s self-defense in a call on Saturday with Saudi Crown Prince Mohammed Bin Salman.

Iran launched an “unprecedented attack on the world’s energy supply,” Pompeo said on Twitter after at least one Republican lawmaker urged the U.S. to respond in kind with a strike on Iranian oil facilities.

“Tehran is behind nearly 100 attacks on Saudi Arabia while Rouhani and Zarif pretend to engage in diplomacy. Amid all the calls for de-escalation, Iran has now launched an unprecedented attack on the world’s energy supply. There is no evidence the attacks came from Yemen”, Pompeo wrote.

He then added in another tweet: “We call on all nations to publicly and unequivocally condemn Iran’s attacks. The United States will work with our partners and allies to ensure that energy markets remain well supplied and Iran is held accountable for its aggression”.

Pompeo said the U.S. will work with allies to ensure the energy market remains well supplied, echoing comments from the White House. He also called on all nations to “publicly and unequivocally condemn Iran’s attacks.”

Iranian-backed Houthi rebels in Yemen claimed responsibility for the strikes, which forced Saudi Aramco to cut daily oil production in half.

The U.S. “strongly condemns today’s attack on critical energy infrastructure,” White House spokesman Judd Deere said in an emailed statement that was also posted on Twitter. The U.S. government “is monitoring the situation and remains committed to ensuring global oil markets are stable.”

Republican Senator Lindsey Graham, a confidant of Trump, earlier urged a decisive U.S. response against Iranian targets.

“It is now time for the U.S. to put on the table an attack on Iranian oil refineries if they continue their provocations or increase nuclear enrichment,” Graham of South Carolina said on Twitter. “Iran will not stop their misbehaviour until the consequences become more real, like attacking their refineries.”

John Abizaid, the U.S. ambassador to Saudi Arabia, said in a tweet “attacks against critical infrastructure endanger civilians, are unacceptable, and sooner or later will result in innocent lives being lost.