U.S. oil prices settled higher than international ones for the first time in nearly four years on Thursday, after President Donald Trump’s address to the nation failed to give investors clarity about when the Iran war will end and the Strait of Hormuz might reopen.

The price of West Texas Intermediate futures, the U.S. benchmark, settled at $111.54, up more than 11% after a volatile day that saw prices rise to as much as $113.97 in the morning.

A slight, late-morning pullback happened just before media outlets reported on an Islamic Republic News Agency headline that said Iran and Oman were drafting a protocol to monitor traffic through the strait. Meanwhile, some 40 nations held a virtual summit to discuss its reopening. The U.S. didn’t attend, AP News reported.

But oil prices soon resumed their ascent as U.K. foreign secretary Yvette Cooper accused Iran of hijacking the international shipping route “to hold the global economy hostage.”

She noted that over the past day, just five vessels had passed through the strait versus the typical 150 during a normal 24-hour period. The vital waterway, through which 20% of the world’s oil previously traversed, has been effectively closed since the start of the war.

Meanwhile, Brent crude futures settled at $109.03 a barrel, down from their earlier high of $109.74 for an increase of 7.8% compared with Wednesday’s settle price.

The U.S. oil price benchmark hadn’t settled above Brent futures since May 18, 2022, according to Dow Jones Market Data.

The shift is mainly down to timing. The WTI market is still trading the May contract as the soonest delivery month, while the Brent market has already rolled over to June. Because investors still aren’t sure how long the war will last, they’re pricing in more supply disruption in May than in June.

Buyers may also be scrambling for oil that is available immediately and outside the zone disrupted by the war in the Middle East. U.S. crude fits that need, driving up demand for WTI-linked barrels.

Trump urged other countries to “buy from the U.S., we have plenty,” in a social media post about nations struggling to get jet fuel as a result of the Strait of Hormuz blockage, earlier this week.

Just two weeks ago, WTI was trading at nearly a $20 discount to Brent crude in intraday trading, but U.S. prices have closed the gap.

Both benchmarks settled lower on Wednesday on hopes that Trump would use his speech to lay out a plan to end the conflict in the Middle East.

That didn’t happen. Trump shed little light on the progress of the war in his address. While he said the U.S.’s core strategic operations were nearing completion, the military is going to hit Iran “extremely hard over the next two to three weeks.”

“Gas prices will rapidly come back down and stock prices will rapidly go back up,” the president said, without providing much further detail. Average gasoline prices nationwide have jumped by more than $1 a gallon over the past month, according to data from the AAA. The S&P 500 is down 4.4% since the conflict started.

Prices at the pump could carry on surging unless the U.S. and its allies are able to swiftly reopen the Strait of Hormuz, the key shipping corridor that Iran has effectively closed since the war started a month ago.

The price of crude could top $150 a barrel if the conflict drags on another month, UBS warned.

“We continue to see near-term risk to the upside for oil and gas prices, as long as we do not have visibility on a meaningful resumption of flows via Hormuz,” UBS analyst Henri Patricot said Thursday in a research note, adding that global oil inventories likely fell to their five-year average at the end of March.

Supplies will carry on dwindling the longer disruption persists and crude prices could top $150 a barrel “if there is no improvement in sight” this month, Patricot wrote.

“The Strait of Hormuz is still effectively closed, and the baseline assumes that it won’t change until the end of April, removing additional oil supply from the market and adding to the economic costs with each passing day,” Oxford Economics’ global chief economist Ryan Sweet said, although Trump’s televised address didn’t shift his forecast that Brent prices will average $113 a barrel over the second quarter.

Hours after Trump’s speech, Iran rejected the idea that its military capabilities had weakened. Such assessments rely on incomplete information or are outright incorrect, a spokesman for Iran’s military joint command told a state-run broadcaster, according to The Wall Street Journal.