US President Donald Trump has warned that Iran would be “blown off the face of the Earth” if it attacks United States ships as tensions around the Strait of Hormuz push the truce between the two countries to the brink.

Hostilities were renewed in the region on Monday as Iran attacked the United Arab Emirates, and Trump said the US military shot down seven small Iranian boats near Hormuz.

In an interview with Fox News, Trump underscored Washington’s military power, and he renewed his threats to Iran.

“We have more weapons and ammunition at a much higher grade than we had before,” he said.

“We have the best equipment. We have stuff all over the world. We have these bases worldwide. They’re all stocked up with equipment. We can use all of that stuff, and we will, if we need it.”

The US military began implementing on Monday a Trump plan – dubbed Project Freedom – to guide ships through Hormuz and break the Iranian blockade on the strategic shipping lanes.

Washington said it helped two US merchant vessels through the strait, but ship-tracking websites show traffic through the waterway remains largely suspended.

Admiral Brad Cooper, the head of the US Central Command (CENTCOM), said vessels stranded in the area belong to 87 countries that are “innocent bystanders” in the conflict.

“Over the last 12 hours, we’ve reached out to dozens of ships and shipping companies to encourage traffic flow through the [Strait of Hormuz], consistent with the president’s intent to help guide ships safely through a narrow trade corridor,” Cooper said in a statement.

But it’s not clear how the vessels responded to the US assurances.

South Korean ship attacked

On Monday, Iran appeared to demonstrate its ability to still target ships near the strait. South Korea confirmed that one of its vessels suffered from an explosion and a fire off the coast of the UAE.

Separately, United Kingdom Maritime Trade Operations (UKMTO) said fires were reported on two ships in the area.

Trump, who has been trying to rally international support for military plans to forcibly open Hormuz, cited the attack on the South Korean ship to urge Seoul to join his campaign.

“Iran has taken some shots at unrelated Nations with respect to the Ship Movement, PROJECT FREEDOM, including a South Korean Cargo Ship. Perhaps it’s time for South Korea to come and join the mission,” the US president wrote in a social media post.

“We’ve shot down seven small Boats or, as they like to call them, ‘fast’ Boats. It’s all they have left. Other than the South Korean Ship, there has been, at this moment, no damage going through the Strait.”

Iran’s official news agency IRNA cited a military source as saying that the “US claim of sinking a number of Iranian warships is false”.

Although the US is largely self-sufficient in oil production, the US-Israel war on Iran, launched on February 28, has sent global energy prices soaring.

The price of one gallon (3.8 litres) of gas or petrol in the US has risen from less than $3 before the war to more than $4.45 on Monday, fuelling inflation months ahead of the crucial midterm elections that will determine control of the US Congress.

Washington’s assurances that it would protect ships in the strait have not dented energy markets. The price of oil internationally and the cost of petrol in the US continued to climb on Monday.

Lebanese news outlet Al Mayadeen cited a senior Iranian official as saying that the administration of the Hormuz Strait remains fully in Tehran’s hands.

“Our message to the Iranian aggressors: Move forward and you will be targeted,” the official said.

Iran strikes UAE

Amid the tensions, Iran renewed its attacks on the UAE on Monday.

The UAE Defence Ministry said the country’s forces engaged 12 ballistic missiles, three cruise missiles and four drones.

The media office in the emirate of Fujairah confirmed that an Iranian attack caused a fire in the Fujairah Petroleum Industry Zone and injured three people.

The UAE and several Gulf countries condemned the Iranian attacks.

“The UAE emphasised that it will not tolerate any threat to its security and sovereignty under any circumstances, and that it reserves its full and legitimate right to respond to these unprovoked attacks,” the UAE Foreign Ministry said in a statement.

An Iranian official told the Islamic Republic of Iran Broadcasting (IRIB) on Monday that the attack on Fujairah was the result of US policy.

“The Islamic Republic had no pre-planned plan to attack the oil facilities in question, and what happened was the product of the American military’s adventurism to create a passage for ships to illegally pass through … the Strait of Hormuz, and the American military must be held accountable for it,” the official said.

While trying to pry open Hormuz, the US has said that its blockade of Iranian ports persists.

CENTCOM said on Monday that “50 commercial vessels have been redirected by US forces to ensure compliance” with the naval siege.