ISTANBUL — Tensions between the United States and Iran ratcheted up Wednesday as Secretary of State Mike Pompeo decried the weekend attacks on the Saudi oil industry as an “act of war” and President Trump ordered a substantial increase in sanctions against the government in Tehran.

With the Trump administration linking the sanctions step to the airstrikes, Iran warned the United States that it would retaliate for any attack against it, Iranian news agencies reported Wednesday. An attack on Iranian territory would be met with a “rapid and crushing” response, the Fars News Agency said.

Five days after the strikes on Saudi oil facilities, which were claimed by a Yemeni rebel group, U.S. and Saudi officials all but explicitly accused Iran of launching the attacks from its territory. They presented physical evidence and other details that they said bolstered their assertions of direct Iranian culpability.

The heightened tensions come after several months of escalating threats in the Persian Gulf, as Iran has sought to intensify pressure on the United States and its allies in response, officials in Tehran say, to the increasingly severe American sanctions crippling the Iran economy.

The initial claim of responsibility for the weekend attacks by the Iranian-allied rebels, known as the Houthis, “doesn’t change the fingerprints of the ayatollah as having put at risk the global energy supply,” Pompeo told reporters, in an apparent reference to Ayatollah Ali Khamenei, Iran’s supreme leader, while traveling to Saudi Arabia. His comments set the tone for a day of developments that raised temperatures across the Persian Gulf.

The attacks on the installations in eastern Saudi Arabia temporarily cut the kingdom’s oil production in half and caused prices to jump worldwide.

The U.S. and Saudi governments have yet to provide solid evidence of where the attacks originated. In the absence of such proof, Iran has forcefully pushed back against the accusations and warned of consequences if it is attacked.

The day’s first salvo came from President Trump, who wrote in a tweet that he had “just instructed the Secretary of the Treasury to substantially increase Sanctions on the country of Iran!” He later told reporters traveling with him in California that “very significant” sanctions would be announced “over the next 48 hours.”

Trump warned of “a very powerful attack” against Iran Wednesday afternoon as he toured the U.S.-Mexico border in Otay Mesa, Calif., near San Diego. He said his plans are “very fluid” and that “a lot of things can happen — rough things and not so rough things.”

Trump told reporters he was being judicious in evaluating whether to respond with military force. “We are doing it the right way,” he said. “We’re doing it the smart way… We will see what we will see.”

But, the president added, “One call and we can go in.”

Yemen’s Houthi rebels, who asserted responsibility for the attacks, have since 2015 been battling a Saudi-led coalition that backs the internationally recognized government in Yemen. The conflict has caused the world’s most severe humanitarian crisis.

The Houthis have repeatedly attacked the kingdom, using ground troops, drones and ballistic missiles, some reaching deep into Saudi territory. They have called the strikes a response to the Saudi-led coalition’s years-long air war over Yemen, which has included thousands of airstrikes that have killed thousands of civilians, according to human rights groups.

U.S. officials, however, have cast doubt on the rebels’ involvement in Saturday’s attacks.

Pompeo, who met with Saudi Crown Prince Mohammed bin Salman on Wednesday evening, told reporters shortly before arriving in Saudi Arabia that the intelligence community had “high confidence” that the weapons systems used in the attacks were not in the Houthis’ arsenal. The attacks had also not come from the south, where the Houthis control territory, he added, citing “flight patterns” that would have explained the location of impact points at the Saudi oil facilities.

“This was an Iranian attack,” he said. “It didn’t come from the Houthis.” The United States also did not have any evidence the attacks came from Iraq, he added, but he did not specify which country had been the launchpad.

A senior administration official familiar with Pompeo’s visit said the U.S. team examined photos and debris, including some intact weaponry.

“That equipment is not used in the Houthi arsenal, including UAVs and the light cruise missiles used,” the official said.

A Saudi military spokesman in Riyadh, the Saudi capital, also presented what he said was evidence of Iran’s fingerprints on the strikes, including remnants of drone and cruise missiles that he said were used in the attacks and were Iranian-made.

The spokesman, Col. Turki al-Malki, said in a news conference that 18 unmanned aerial vehicles had attacked an oil processing plant in Abqaiq in eastern Saudi Arabia. Seven cruise missiles, he added, were fired at a facility in Khurais, the site of one of the kingdom’s largest oil fields. Three of the cruise missiles fell short, he said.

The attacks were “unquestionably sponsored by Iran” and had not originated in Yemen, Malki said, basing the assertion in part on the purported range of the weapons recovered, which he said could not have traveled from Houthi-held territory. But Saudi officials had not determined from where the weapons were launched.

Malki did not say how the launch site would be identified but said there would be “accountability” when it was.

Iran delivered its warning to the United States via the Swiss Embassy in Tehran, which handles U.S. affairs in Iran. The official message condemned remarks by Pompeo and other officials linking Iran to the attacks.

“Iran’s response will be prompt and strong, and it may include broader areas than the source of attacks,” the Mehr News Agency reported the official note as saying.

Iran’s Fars News Agency said any response to an attack would target “more extensive areas than the origin of the attack.” There have long been fears that Iranian proxy forces in Lebanon, Syria, Iraq and elsewhere might attack U.S. forces in the region.

The Iranian mission to the United Nations declined to comment on Trump’s tweet but a spokesman repeated an assertion that “the U.S. economic terrorism is illegal.” Iran considers U.S. sanctions to violate the U.N. Security Council resolution that endorsed the 2015 nuclear deal, which was signed between Iran and world powers, including the United States but which the United States has disavowed under Trump.

The Treasury Department’s Office of Foreign Assets Control, which administers U.S. sanctions, already lists 674 Iranian entities, vessels and individuals who have been sanctioned. The list includes banks, pension funds, tanker and shipping companies, cement plants, aircraft, the national oil company, judges and even a prison. The most prominent targets are the Islamic Revolutionary Guard Corps and Foreign Minister Mohammad Javad Zarif.

Though a number of potential targets are always kept in reserve, some experts wondered what remains to be sanctioned.

“If there really was much more they could sanction that would have a significant impact, I don’t see why they would not have done it already,” said Trita Parsi, the executive vice president of the Quincy Institute.

Meanwhile, the United States still has not issued visas for Iranian President Hassan Rouhani and his delegation to go to New York next week for the United Nations General Assembly, and the Iranians may cancel their trip, state media reported Wednesday.

Pompeo declined to discuss visas for Rouhani and Zarif, whom the United States sanctioned in July. Under a 1947 agreement, the United States as the “host country” of the United Nations must admit diplomats of foreign countries to attend if they are on official U.N. business, but Washington says it can deny visas for national security, terrorism or foreign policy reasons.

“If you’re connected to a foreign terrorist organization, I don’t know, it seems to me it would be a reasonable thing to think about whether they ought to be prevented to attend a meeting which is about peace,” Pompeo told the reporters traveling with him to Saudi Arabia.


Morello and Wagner reported from Washington. Paul Schemm in Dubai, Anne Gearan in Washington and Philip Rucker in Otay Mesa, Calif., contributed to this report. 

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