Donald Trump said on Friday that US forces have “obliterated” military targets in a raid on Iran’s Kharg Island and warned that crucial oil infrastructure there could be next, in the latest escalation of the war of words between Washington and Tehran.

“For reasons of decency, I have chosen NOT to wipe out the Oil Infrastructure on the Island,” Trump wrote on social media. “However, should Iran, or anyone else, do anything to interfere with the Free and Safe Passage of Ships through the strait of Hormuz, I will immediately reconsider this decision.”

The flow of oil and gas from Iran and the Gulf has moved centre stage in the ongoing conflict in recent days.

Kharg lies 25kms off Iran’s coastline, and is the main facility for the export of the country’s oil. Iran has effectively closed the narrow strait of Hormuz, through which a fifth of the world’s traded oil passes, sending oil prices surging and raising the prospect of massive damage to economies worldwide.

In a post on his Truth Social platform, Trump also called on “Iran’s Military, and all others involved with this Terrorist Regime” to “lay down their arms, and save what’s left of their country, which isn’t much!”. He also accused what he calls “The Fake News Media” of failing to accurately portray the joint US-Israeli offensive, launched two weeks ago.

The US president’s comments prompted a defiant response from Iran, where senior military officials reiterated a threat to attack any US-linked oil and energy facilities across the Middle East if the oil infrastructure of the Islamic Republic were hit.

Iran has so far responded to the joint US-Israeli offensive, which is entering its third week, with daily attacks on oil and other infrastructure around the Gulf region, as well as against Israel.

Ebrahim Zolfaghari, spokesperson for Iran’s joint military command, warned of attacks on “all oil, economic and energy infrastructures belonging to oil companies across the region that have American shares or cooperate with America.”

More than 1,400 are reported to have been killed in Iran, where residents report relentless bombing. Thirteen have been killed in Israel, and about 20 in the Gulf.

In his first public comments, Iran’s new supreme leader, Mojtaba Khamenei, last week vowed to keep the strait of Hormuz shut and urged neighbouring countries to close US bases on their territory or risk being attacked themselves.

No images have been released of Khamenei since an Israeli strike at the start of the war that killed much of his family, including his father and wife. Iran says the new supreme leader was wounded, but an official said on Friday he was not “impaired.”

Trump on Friday declined to publicly give an end date for the conflict, telling reporters: “It’ll be as long as it’s necessary.”

Analysts have suggested that Trump will seek to end the conflict soon to prevent a deep global economic crisis.

Experts told the Guardian earlier this week that military actions against Kharg Island would lead to a further dramatic spike in oil prices, already surging since the war began on 28 February.

“We may see the $120 a barrel price we saw on Monday heading to $150 if Kharg were attacked,” said Neil Quilliam of the Chatham House thinktank. “It’s too vital for global energy markets.”

Last week, Trump called the radical Islamist leaders of Iran “deranged scumbags” and said it was an honour to kill them. Pete Hegseth, the US defence secretary, told a press conference in Washington that Iranian leaders were “desperate and hiding, they’ve gone underground”.

Hegseth also said that Mojtaba Khamenei was wounded and likely disfigured.

On Saturday, multiple alarms sounded in Israel, warning of incoming missiles and drones launched by Iran and Hezbollah, the Tehran-backed militant Islamist movement in Lebanon.

Gulf states reported continuing Iranian drone and missile attacks directed against both US bases and civilian infrastructure.

In Lebanon, the humanitarian crisis deepened, with nearly 800 people killed and 850,000 displaced, as Israel launched waves of strikes against Hezbollah and warned there would be no let up.

Concerns that the US might seize Kharg Island rose when officials in Washington said that 2,500 more marines and the amphibious assault ship USS Tripoli had been ordered to the Middle East.

Marine expeditionary units are able to conduct amphibious landings, but they also specialise in bolstering security at embassies, evacuating civilians and disaster relief. The deployment does not necessarily indicate that a ground operation is imminent or will take place.

US forces have suffered casualties, including the deaths of all six crew members aboard a refuelling aircraft that crashed in western Iraq.