Iran's military on Monday warned the United States against approaching or entering the Strait of Hormuz, shortly after US President Donald Trump unveiled a new naval operation to guide stranded commercial vessels through the chokepoint. The move marks a fresh escalation in tensions, even as a fragile three-week ceasefire remains largely in effect.

"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," Trump said in a social media post on Sunday night. He said operations would begin on Monday, threatening that any Iranian interference would trigger forceful US response.

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

In response, Iran stressed that all maritime passage through the strategic 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, disrupting global supplies of oil, gas and fertilizer, while the US has maintained a parallel naval blockade on Iranian ports.

According to maritime intelligence firm AXSMarine, over 900 commercial vessels remained stranded in the Gulf as of April 29, down from more than 1,100 at the start of the conflict.

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.

Shortly after Trump's announcement, the UK Maritime Trade Operations reported a tanker was hit by unknown projectiles nearly 140 kilometers north of Fujairah in the United Arab Emirates. All crew members were safe, though few details were immediately available.

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

Global equity markets edged higher on Monday while crude oil prices remained stable after surging back above $100 a barrel last week amid uncertainty over when and how the conflict will end.

Raman Kapoor, an oil tanker captain whose vessel remains stranded in the Gulf, has told Al Jazeera that no ships are likely to attempt crossing the Strait of Hormuz under the present 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 fuel, food and water, other commercial ships were not able to.

Meanwhile, Iranian state media reported that Washington has delivered a response to Iran's 14-point proposal via Pakistan, which Tehran was now reviewing. There was no immediate confirmation from Washington or Islamabad of the US response.

The 14-point proposal includes withdrawing US forces from nearby areas, lifting the blockade, releasing frozen assets, paying compensation, lifting sanctions, ending the war on all fronts including Lebanon and creating a new control mechanism for the strait.

"At this stage, we do not have nuclear negotiations," state media quoted Iran's Foreign Ministry spokesman Esmaeil Baghaei as saying.

According to observers, the proposal to delay talks on nuclear issues until a later phase would appear at odds with Washington's repeated demand that Iran accept stringent restrictions on its nuclear program as a prerequisite for ending the war.

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

cuihaipei@chinadaily.com.cn