Cairo. The standoff over the Strait of Hormuz escalated again on Saturday as Iran reversed its reopening of the crucial waterway and fired on ships attempting to pass, in retaliation after the United States pressed ahead with its blockade of Iranian ports.

The strait is closed until the US blockade is lifted, Iran's Revolutionary Guard navy said Saturday night, warning that “no vessel should make any movement from its anchorage in the Persian Gulf and the Sea of Oman, and approaching the Strait of Hormuz will be considered as cooperation with the enemy” and be targeted.

New attacks on the strait, through which roughly one-fifth of the world’s oil normally passes, threatened to deepen the global energy crisis and push the countries into renewed conflict as the war entered its eighth week.

A fragile ceasefire is due to run out by Wednesday. Iran said it had received new proposals from the United States, and Pakistani mediators were working to arrange another round of direct negotiations.

Iran’s joint military command earlier said “control of the Strait of Hormuz has returned to its previous state ... under strict management and control of the armed forces.”

Revolutionary Guard gunboats opened fire on a tanker and an unknown projectile hit a container vessel, damaging some containers, the British military’s United Kingdom Maritime Trade Operations center said. India's foreign ministry said it summoned Iran's ambassador over the “serious incident” of firing on two India-flagged merchant ships, especially after Iran earlier let several India-bound ships through.

For Iran, the strait's closure -- imposed after the U.S. and Israel launched the war on Feb. 28 during talks over Tehran's nuclear program -- is perhaps its most powerful weapon, threatening the world economy and inflicting political pain on President Donald Trump. For the United States, the blockade keeps up pressure and could strangle Iran's already weakened economy.

Iran’s new supreme leader, Ayatollah Mojtaba Khamenei, issued defiant remarks on Saturday, saying the navy stands “ready to inflict bitter defeats on its enemies.” He has not been seen in public since being elevated to the post following his father's death in Israel’s opening barrage.

On Friday, Iran announced the strait's reopening to commercial vessels after a 10-day truce was announced between Israel and the Iranian-backed Hezbollah militant group in Lebanon. The reopening caused oil prices to fall.

Trump, however, said the US blockade of Iran's ports “will remain in full force” until Tehran reaches a deal with the United States. Trump had imposed the blockade after a round of historic face-to-face talks in Pakistan between the countries ended without an agreement.

US forces have sent 23 ships back to Iran since the blockade began on Monday, US Central Command said Saturday. Trump's comments triggered an outcry.

“Americans are risking the international community, risking the global economy through these, I can say, miscalculations,” Iranian Deputy Foreign Minister Saeed Khatibzadeh told The Associated Press, adding that the US is “risking the whole ceasefire package.”

Iran’s Supreme National Security Council issued a statement calling the blockade a violation of the ceasefire and said Iran would prevent “any conditional and limited reopening” of the strait. The council has recently acted as Iran’s de facto top decision-making body.

Since most supplies to US military bases in the Gulf region come through the strait, “Iran is determined to maintain oversight and control over traffic through the strait until the war fully ends,” the council said. That means Iran-designated routes, payment of fees, and issuance of transit certificates.

The Revolutionary Guard Navy statement later indicated that no vessel should attempt a transit at all.