Iran reversed its decision to reopen the Strait of Hormuz and warned that it would continue to block transit through the strait as long as the U.S. blockade of Iranian ports remained in effect.

The escalating standoff over the critical choke point threatened to deepen the energy crisis roiling the global economy and push the two countries toward renewed conflict, even as mediators expressed confidence that a new deal was within reach.

The strait is closed until the U.S. blockade is lifted, Iran’s Revolutionary Guard navy said Saturday night. Hours earlier, two gunboats from Iran’s Revolutionary Guard opened fire on a tanker transiting the Strait of Hormuz, the British military’s United Kingdom Maritime Trade Operations center said. It reported that the tanker and crew were safe, without identifying the vessel or its destination.

Roughly one-fifth of the world’s oil passes through the strait and further limits would squeeze the already constrained supply, driving prices higher once again. Meanwhile, a 10-day truce between Israel and the Iran-backed Hezbollah militant group in Lebanon appeared to be holding.

The fighting in the Middle East conflict, which is approaching the two-month mark, has killed at least 3,000 people in Iran, nearly 2,300 in Lebanon, 23 in Israel and more than a dozen in Gulf Arab states. Thirteen U.S. service members have also been killed.

Iran negotiator says strait will remain closed

Iran’s parliamentary Speaker Mohammed Bagher Qalibaf says the Strait of Hormuz will remain closed as long as the U.S. imposes a naval blockade on Iran.

“It is impossible for others to pass through the Strait of Hormuz while we cannot,” he said in televised comments aired by Iranian semiofficial media late Saturday.

Qalibaf, who is Iran’s chief negotiator with the United States, said that the strait is now under Iran’s control, linking the choke point’s reopening to the U.S. lifting of its blockade.

“If the U.S. does not lift the blockade, traffic in the Strait of Hormuz will definitely be restricted,” he said.

He said that the ceasefire was on verge of collapse when the U.S. attempted to mine-clear the strait.

He said Iran viewed the U.S. attempt as a violation of the ceasefire.

“The situation escalated to the point of conflict but the enemy retreated,” he said.