The U.S. denied a report by Iranian media on May 4 that the country had struck an American naval vessel with missiles, Axios reported citing a senior official. Oil prices and stocks pared back some of their earlier moves.

Brent crude had jumped around 5% to over $113 a barrel and stocks fell after Fars reported a strike on a U.S. frigate near the Gulf of Oman port of Jask following ignored warnings from the Islamic Republic’s navy. The U.S. boat was forced to retreat and flee the area, Fars reported, citing unnamed sources. 

Shortly before, Tasnim, another Iranian news agency, announced the government had “redefined the control zone” in the Strait of Hormuz and effectively set out maritime borders within which Tehran would regulate shipping traffic.

The developments added to tensions, hours after President Donald Trump said the U.S. will help ships stranded in the Persian Gulf transit the strait, describing it as a “humanitarian gesture.”

The operation, dubbed Project Freedom, was set to begin on May 4, with the U.S. military pledging to provide support, including the use of guided-missile destroyers, aircraft and drones.

“The Ship movement is merely meant to free up people, companies, and Countries that have done absolutely nothing wrong — They are victims of circumstance,” Trump wrote late Sunday in a social media post. “If, in any way, this Humanitarian process is interfered with, that interference will, unfortunately, have to be dealt with forcefully.”

Trump said some of the ships stranded in the Persian Gulf have large crews that are running out of food while they’re waiting for safe passage through Hormuz. He said that several countries have asked the U.S. for help in freeing up their ships.

The plan has left shipping executives perplexed, with few details provided by the president. Iran’s military, after Trump’s announcement, had said U.S. forces would be attacked if they entered the Strait of Hormuz, according to a statement carried by Iranian broadcaster Press TV.

An “enhanced security area” has been established by the U.S. to support transits, according to the Joint Maritime Information Center on May 4. JMIC, a multinational body that analyzes security threats in the area, advised vessels to consider crossing the waterway through Omani waters. It warned of the presence of mines north of Omani waters.

There were more reports of attacks on ships. A tanker reported being hit by projectiles roughly 80 miles north of the UAE port Fujairah on May 3, according to the U.K. Maritime Trade Operations, which provides security updates for the region. That’s less than a day after a report of a bulk carrier being attacked by small boats.

Trump’s announcement came amid an impasse between Iran and the U.S. A shaky ceasefire has been in place since April 7, with the sides struggling to agree to peace talks. Trump, in the same Truth Social post, talked of ongoing discussions with Iranian authorities that “could lead to something very positive for all.”

He has struck a similar tone in recent weeks, but negotiations have yet to break the deadlock. 

At the center of the dispute is Hormuz, where Iran has blocked almost all vessel traffic. It says it will only reopen the strait after the U.S. lifts a naval blockade on Iranian ports. Washington wants Tehran to move first and believes its restrictions are squeezing Iran’s economy and will force Tehran to make concessions.

Here’s more on the war:

• Oil rose Monday, with Brent up 3.9% to just over $112 a barrel.
• Iran is reviewing a U.S. response to its recent 14-point plan to end the war, Iranian TV reported on Sunday, citing a foreign ministry spokesman.
• Over the weekend, Trump suggested that proposal would not be enough to satisfy him. Iran’s Tasnim News Agency reported the plan called for a complete end to the conflict within 30 days along with guarantees against renewed strikes on Iran. It said the plan reiterates Tehran’s earlier demands, including that U.S. forces withdraw from near Iran, the maritime blockade be lifted, sanctions removed, and reparations paid. The nuclear issue wasn’t mentioned.
• China has ordered its companies to ignore U.S. sanctions on private refiners linked to the Iranian oil trade, an unprecedented act of defiance that threatens to trap a vast banking sector in the crossfire as tension rises between the world’s largest economies.
• It’s highly likely that the European Central Bank will have to raise interest rates at its next meeting in June, Governing Council member Peter Kazimir said. The comments underscored the pressures on central bankers as the war causes fuel prices to surge.