A tanker came under attack trying to leave the Persian Gulf and Treasury Secretary Scott Bessent threatened tougher restrictions on Iran's economy, pushing oil prices higher. Brent crude prices are up just under 1% at around $88 a barrel. The oil benchmark has gained more than 5% so far this week.

The tanker sustained minor damage from an unmanned aerial vehicle, according to a U.K. naval agency that tracks incidents in commercial shipping. The agency didn't name the ship or attribute responsibility. Iranian attacks have reduced traffic through the Strait of Hormuz despite President Trump's claim that the U.S. has control of the waterway.

Late Thursday, Newsmax published an interview with Bessent in which the Treasury secretary said the U.S. would announce new financial measures against Iran next week. "We are going to apply measures like have never been seen in the history of the economic isolation of a country," he said.

Washington already has strict sanctions in place on Iran's oil sales as it tries to force the country's leaders to capitulate. Iran has responded by rationing scarce goods, limiting access to foreign currency and slashing investment.

"It is becoming increasingly difficult to identify sanctions that could still have an effect and have not already been introduced," said Arne Lohmann Rasmussen, chief analyst at Danish trading firm Global Risk Management.