A United States Navy vessel reportedly came under Iranian missile fire near the Strait of Hormuz on Monday after it ignored warnings to halt, but the US military denied that any warship had been struck.

Iran's semiofficial Fars News Agency reported that two missiles targeted the US frigate as it sailed near Iran's Jask Port and attempted to navigate the strait. The outlet added the vessel failed to continue its voyage and was forced to withdraw from the waters.

The reported attack came hours after Washington unveiled a new operation to guide stranded commercial ships through the strait, following Tehran's warning against the US military approach or entry into the waterway.

"We have told these countries that we will guide their ships safely out of these restricted waterways, so that they can freely and ably get on with their business," US President Donald Trump said on Sunday.

Operations would begin on Monday, he said, threatening that any Iranian interference would trigger a forceful US response.

US media outlets The Wall Street Journal, CNN and Axios highlighted Trump's chosen word of "guide" rather than "escort" to describe how the so-called Project Freedom will work, though Trump gave few details. Axios quoted a US official as saying that US Navy ships will be "in the vicinity" to prevent Iranian attacks on the commercial ships.

In response, Iran said all maritime passage through the strait must be coordinated with its military.

"We warn that any foreign armed force — particularly the aggressive US military — will be targeted and attacked if it attempts to approach or enter the Strait of Hormuz," Ali Abdollahi, chief commander of Iran's Khatam al-Anbiya Central Headquarters, told state broadcaster IRIB.

Iran has enforced tight control over the strait since the war began on Feb 28, disrupting global oil, gas and fertilizer supplies, while the US has maintained a parallel naval blockade on Iranian ports.

Stranded ships

According to maritime intelligence firm AXSMarine, more than 900 commercial vessels were stranded in the Persian Gulf as of April 29, down from over 1,100 recorded when the conflict started.

US Central Command said it would support the effort with 15,000 military personnel, more than 100 land and sea-based aircraft, along with warships and drones.

The vital waterway has remained largely blocked since late February, cutting off the transit of 20 percent of the world's oil and gas and fueling a steep rally in global energy prices. A ceasefire took effect on April 8, and one round of direct US-Iran peace talks has since been held in Islamabad, Pakistan, yet both sides remained deadlocked over core demands.

Global equity markets edged higher on Monday, while crude oil prices were little moved, having surged back above $100 a barrel last week.

Raman Kapoor, an oil tanker captain whose vessel is stranded in the Gulf, told Al Jazeera that no ships were likely to attempt crossing the Strait of Hormuz under current conditions.

"No ships would want to show their courage and pass through the strait unless it is officially declared safe to transit," he said, adding that while his vessel was able to restock in fuel, food and water, other commercial ships were not able to.

Meanwhile, Iranian state media said Washington had delivered its response to Tehran's 14-point proposal via Pakistan, and that Iran was reviewing it. There was no immediate confirmation from Washington or Islamabad of the US response.

"At this stage, we do not have nuclear negotiations," Iranian Foreign Ministry spokesman Esmaeil Baghaei was quoted by state media as saying.

Observers said the proposal to delay nuclear talks until a later phase would appear at odds with Washington's repeated demand that Iran accept stringent restrictions on its nuclear program before the war can end.

Shi Guang in New York and agencies contributed to this story.

cuihaipei@chinadaily.com.cn