U.S. oil prices jumped back above $100 a barrel Monday after failed talks between Washington and Tehran and a new order by Donald Trump to impose a blockade on Iranian ports.

West Texas Intermediate for May delivery rose about 8% to $104.50 shortly after trading opened, while Brent crude for June delivery climbed 7% to $102.

Asian markets fell in early trading. South Korea’s Kospi dropped 2% before trimming losses, while Japan’s Nikkei slipped 0.3%.

Oil had declined and equities rallied last week after Trump agreed to a two-week ceasefire mediated by Pakistan. That truce quickly appeared fragile as Israel continued strikes in Lebanon and the Strait of Hormuz remained effectively closed.

Negotiations in Islamabad on a longer-term agreement, led by U.S. Vice President JD Vance and Iran’s parliament speaker, ended without a deal, with both sides signaling pessimism.

Trump later said he would order a blockade tied to the Strait of Hormuz. The U.S. military said the measure would begin Monday and apply only to vessels traveling to or from Iranian ports.

Markets have been volatile since the conflict began Feb. 28. Iran has effectively blocked the Strait of Hormuz, a critical chokepoint through which about one-fifth of global oil and gas supplies typically pass.