However, Iranian vessels are said to be using Hormuz to ship oil to China: File Image/Pixabay

Iran’s new leader Mojtiaba Khamenei on Thursday vowed to keep the Strait of Hormuz closed and maintain attacks on regional U.S, bases, causing oil prices to climb back above $100 per barrel.

Also spooking oil traders were signs that the  military campaign against the Islamic republic may take longer than U.S. president Donald Trump anticipated: the United Nations claimed that as many as 3.2 million Iranians have been forced out of their homes by the war, while over 1,300 Iranians have been killed, along with 687 Lebanese, 12 Israelis and seven U.S. soldiers.

Eurasia Group president Ian Bremmer wrote on Thursday that Iranian tankers "are still passing through" the Hormuz, bringing oil to China and revenue to Iran.

For its part, the Islamic Revolutionary Guard Corps threatened to set the region’s oil and gas infrastructure “on fire” if Iranian energy sites are attacked.

West Texas Intermediate settled up 9.7 percent on the day to about $97 per barrel, while Brent settled up 9.2 percent, touching $100 per barrel (at peak it reached $101.59).

Addressing a plunge in U.S. stocks due to the Middle East hostilities, Ryan Detrick, chief market strategist at Carson Group, said, "There’s a realization that a resolution to the Middle East conflict is being pushed further out: it’s a sell first, ask questions later type of mentality…there hasn't been safe sector outside of energy."

Detrick added, "Under the surface of soaring crude prices is the realization that the likelihood of [U.S. Federal Reserve] cuts later this year is quickly dwindling."

Oxford Economics said that "the swings in Brent crude oil prices over the past several days are eye-catching and odds are volatility will remain because of the absence of a timeline for when the conflict will de-escalate and when the Strait of Hormuz….will see traffic begin to recover," and it predicted   that oil prices will spike as high as $140 per barrel.

Meanwhile, media reported that Trump is considering a 30-day waiver of a maritime law to combat high oil and fuel prices; if enacted, it would allow foreign tankers to move oil, gasoline, diesel, liquefied natural gas, and fertilizer between U.S. ports, which is normally prohibited under U.S. law.

However, estimates suggest the waiver could slow gasoline price increases by only 5 to 10 cents per gallon.