Fighting between the United States and Iran intensified again around the Strait of Hormuz on Friday, with renewed maritime clashes and missile attacks on the United Arab Emirates, threatening efforts to formalize a ceasefire reached last month.

Iranian media reported sporadic confrontations between Iranian forces and US vessels in the strategic waterway, while the US military said it struck two Iran-linked vessels attempting to enter an Iranian port, forcing them to turn back.

The confrontation also spilled beyond the waterway. The UAE said its air defenses intercepted two ballistic missiles and three drones launched from Iran on Friday, with three people sustaining moderate injuries. Iran did not confirm responsibility for the attack.

Oil prices rose amid the renewed tensions, with Brent crude climbing above $101 a barrel, although prices remained lower for the week overall.

The latest violence marked the most serious flare-up since a ceasefire announced on April 7 following the war that began with joint US-Israeli strikes on Iran on February 28. Iran has largely restricted shipping through the Strait of Hormuz since the outbreak of the conflict, prompting the US to impose a blockade on Iranian ports and escort vessels through the route, which normally handles about one-fifth of global oil supply.

A CIA assessment reportedly concluded that Iran could endure a US blockade of its ports for four months without facing crippling economic consequences, highlighting the challenges Washington faces in trying to pressure Tehran into a lasting settlement.

The escalation came as Washington awaited Tehran's response to a US proposal aimed at formally ending the conflict before broader negotiations on issues including Iran's nuclear program.

US Secretary of State Marco Rubio said in Rome that Washington expected developments within hours, while Iran's Foreign Ministry said it was still reviewing messages exchanged through Pakistani mediation.

Rubio, after meeting Italian Prime Minister Giorgia Meloni, pressed Italy and other US allies over their reluctance to support Washington's efforts to restore shipping access through the strait.

"Are you going to normalize a country claiming to control ​an international waterway? Because if you normalize that, you've set a precedent that's going to get repeated in a dozen other places," he ​said.

As tensions mounted, Iran accused Washington of breaching the ceasefire and undermining diplomatic efforts through military action.

"Every time a diplomatic solution is on the table, the US opts for a reckless military adventure," Foreign Minister Seyed Abbas Araghchi said on Friday, as Iranian media reported that a US naval strike on an Iranian merchant vessel late Thursday left one crew member dead, 10 injured and four others unaccounted for.

Tehran also warned that future US naval blockade measures would be met with military action, according to Iran's semi-official Fars news agency citing a lawmaker.