Sept. 15 (UPI) -- One day after 10 drone attacks knocked out half of Saudi Arabia's oil output, U.S. President Donald Trump said Sunday night they "believe that we know the culprit, are locked and loaded" with a response.
In a Twitter post, Trump didn't name who was responsible for disrupting 5 percent of daily global oil supply though his U.S. Secretary of State, Mike Pompeo, on Saturday alleged Iran was behind the attacks, which have already resulted in a double-digit spike in crude oil and gas futures.
"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!" Trump posted on Twitter on Sunday night.
Yemen's Houthi rebels, who have received material support from Iran, have claimed responsibility for the attacks, which took place around 4 a.m. local time Saturday. They have been engaged in a bloody war with Saudi Arabia since Riyadh launched an offensive in Yemen in 2015.
Iran Foreign Minister Javad Zarif on Sunday refuted the allegations. "Having failed at 'max pressure', @SecPompeo's turning to 'max deceit'," Zarif posted on Twitter. He was referring to the Trump administration's "maximum pressure" policy of sanctions on Iran.
"Blaming Iran won't end disaster. Accepting our April '15 proposal to end war & begin talks may," Zarif added.
Iran's Foreign Ministry spokesman Abbas Mousavi said earlier that "such useless accusations ... are meaningless and not comprehensible and are pointless."
Pompeo specifically named President Hassan Rouhani and Zarif while blaming Iran for the attack.
"Tehran is behind nearly 100 attacks on Saudi Arabia while Rouhani and Zarif pretend to engage in diplomacy," Pompeo posted on Twitter. "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.
"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."
A Yemeni military spokesman told the Houthi-run Al-Masirah news agency it was a "large-scale" attack with drones that hit its targeted Saudi Aramco oil facilities in Abqaiq and Khurais.
It's the biggest attack carried out on Saudi oil infrastructure since Saddam Hussein's scud missile attacks during the first Gulf War in 1990.
After the attacks, Saudi Arabia halted oil production of 5.7 million barrels of crude oil per day.
"Abqaiq is the heart of the system; it just had a heart attack," Roger Diwan, oil consultant at IHS Markit, told The Guardian. "We just don't know the severity."
Officials at Saudi Aramco, the kingdom's state oil giant and the world's largest company, will likely deliver a report Monday after assessing the damage. The fires were under control and authorities were investigating, the Saudi Interior Ministry tweeted.
They are investigating the possibility that the attacks involved cruise missiles, the Wall Street Journal reported.
Saudi Aramco, which pumped about 9.8 million barrels a day in August, will be able to keep customers supplied for several weeks by drawing on a global storage network.
The Saudis have millions of barrels in tanks in the kingdom, Rotterdam in the Netherlands, Okinawa in Japan and Sidi Kerir on the Mediterranean coast of Egypt.
A protracted disruption in production "could be a big challenge for the oil markets," Mele Kyari, chief executive officer of state producer Nigerian National Petroleum Corp., told Bloomberg Television on Sunday.
U.S. crude, known as WTI, traded at $60.97 per barrel Sunday night, up 11.2 percent after closing at $54.85 on Friday, according to Business Insider. Brent crude, the benchmark used in European oil markets, traded at $67.97 a barrel, compared with $60.22 at Friday's close, a 12.8 percent spike.
November gasoline futures were up 11 percent to $1.704, according to Barchart.
The average price of gasoline in the United States is $2.56 -- virtually the same as last week, according to AAA.
"The global economy can ill afford higher oil prices at a time of economic slowdown," Ole Hansen, head of commodities strategy at Saxo Bank A/S in Copenhagen, said in an email to Bloomberg News.
Saudi Arabia's economy is heavily dependent on oil. Its benchmark stock index tumbled as much as 3.1 percent Sunday in Riyadh.
The loss of 5.7 million barrels a day is the worst supply disruption ever, surpassing the loss of Kuwaiti and Iraqi petroleum supply in August 1990 before the first Gulf War, and Iranian oil output in 1979 during the Islamic Revolution, according to data from the U.S. Energy Department.
Although Trump tweeted there is "PLENTY OF OIL!" he said the shortfall may impact oil prices.
"I have authorized the release of oil from the Strategic Petroleum Reserve, if needed, in a to-be-determined amount sufficient to keep the markets well-supplied," he tweeted. "I have also informed all appropriate agencies to expedite approvals of the oil pipelines currently in the permitting process in Texas and various other States."
Around 630 million barrels are in the reserves, "exactly for this purpose," Department of Energy spokesperson Shaylyn Hynes said in a statement Saturday.
Energy Secretary Rick Perry also has directed his agency to work with the International Energy Agency "on potential available options for collective global action if needed."
Trump called Saudi Crown Prince Mohammad bin Salman on Saturday to offer his support for the kingdom.
"Violent actions against civilian areas and infrastructure vital to the global economy only deepen conflict and mistrust," Deere said.
Since Trump withdrew from the 2015 Iran nuclear deal and re-imposed sweeping sanctions on Iran last year, tensions have risen between the two nations.
On Sunday, a top Iranian commander warned that Tehran has the capability of launching advanced missiles at U.S. bases and aircraft carriers within a range of 1,242 miles.
"We have constantly prepared ourselves for a full-fledged war," Gen. Amirali Hajjizadeh, the head of Iran's Revolutionary Guards Corps Aerospace Force, was quoted by the semi-official Tasnim news agency.
He made no direct mention of the attacks in Saudi Arabia.
The commander noted that the IRGC Aerospace Force was on high alert after Iran shot down a U.S. spy drone over the Persian Gulf on June 20. He said Iranian missiles were zeroed in on Al Udeid Air Base in Qatar, Al Dhafra Air Base in the United Arab Emirates and an American warship in the Sea of Oman.
"We would have hit those targets if the U.S. had shown a reaction," Hajjizadeh said.