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 chokepoint threatened to deepen the energy crisis roiling the global economy and push the two countries toward renewed conflict, even as mediators expressed confidence 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 the tanker and crew as 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 already constrained supply, driving prices higher once again. Iran’s Friday announcement about the opening of the crucial body of water came as a 10-day truce between Israel and the Iranian-backed Hezbollah militant group in Lebanon appeared to hold.

The fighting 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.

Here is the latest:

Israel’s military says another soldier died in combat in southern Lebanon, the second death announced in under twelve hours.

It brought the total number of soldiers killed in Lebanon to 15, and was the second soldier killed in combat since the ceasefire.

The military said another soldier was badly wounded in the same incident, along with four moderately wounded and four lightly injured.

The navy of Iran’s Revolutionary Guard Corps said it extended the closure to the corridor it had earlier designated for the safe passage of vessels through the strategic waterway and declared the strait fully closed until the U.S. blockade on Iranian ports and ships is lifted.

On Friday, Iran said vessels could move through the strait in coordination with it and against the payment of a toll.

But in a statement late Saturday carried by Iran’s state media, the navy warned that any violating vessel would be targeted.

Iran considers the U.S. blockade a violation of the ceasefire between the two countries. Two vessels were attacked earlier on Saturday in the Strait of Hormuz and off Oman’s coast, at least one of them by Iranian gunboats.