Washington expects its operation against Iran to conclude in “weeks, not months”, the US secretary of state has said, despite spiralling violence across the region and a threat from Israel to “escalate and expand” its attacks against the Islamic republic.

“When we are done with them here in the next couple weeks, they will be weaker than they’ve been in recent history,” Marco Rubio told reporters on Friday after meeting G7 foreign ministers in France.

US officials have given conflicting signals about how long they anticipate continuing their joint offensive with Israel against Iran, which began with a surprise strike on 28 February that killed Iran’s supreme leader, Ali Khamenei.

Iran remains defiant, and has denied Donald Trump’s claims that talks are “going well”, saying no negotiations are taking place.

In the Lebanese capital, Beirut, a pre-dawn Israeli strike killed two people, according to local authorities, while barrages of Iranian missiles and drones targeted Israel.

“Despite the warnings, the firing continues,” Israel Katz, the Israeli defence minister, said. “And therefore attacks in Iran will escalate and expand to additional targets and areas that assist the regime in building and operating weapons against Israeli citizens.”

Israel’s most recent strikes targeted nuclear facilities in Iran on Friday, possibly in an attempt to hit what are seen as strategically important targets before the White House forces Israel to halt or reduce sorties.

With stock markets reeling and economic fallout from the war extending far beyond the Middle East, Trump is under growing pressure. It is caused by Iran’s continuing chokehold on the strait of Hormuz, a strategic waterway through which a fifth of the world’s oil is usually shipped.

The Islamic Revolutionary Guard Corps (IRGC) said it had turned back three ships trying to transit the strait, adding that all shipping “to and from ports of allies and supporters of the Israeli-American enemies” was prohibited from passing the strait.

“This morning, following the lies of the corrupt US president claiming that the strait of Hormuz was open, three container ships of different nationalities … were turned back after a warning from the IRGC navy,” the Guards said on their Sepah News website.

Rubio said ensuring the strait remained open to shipping was likely to pose an “immediate challenge” even after the US accomplished its military objectives in Iran. He said Iran might seek to set up a toll on the strait, which he said could cause economic damage to many countries.

“Not only is this illegal, it’s unacceptable … And it’s important that the world have a plan,” Rubio said.

The US has ordered thousands of US marines and elite airborne troops to the region, possibly in preparation for a military effort to forcibly reopen the waterway by seizing one of the many islands in the Gulf or Kharg Island, which is Iran’s principal oil export hub.

On Friday, Esmael Saghab Esfahani, Iran’s vice-president, threatened to attack Saudi Arabia’s Red Sea port of Yanbu, as well as the vast coastal Fujairah oil complex in the United Arab Emirates, should any ground invasion take place.

“Step onto Iranian soil, and $150 becomes the floor for oil,” Esfahani wrote on X.

Trump has also issued Iran with an ultimatum, saying that if it does not allow free passage of shipping through the strait by 6 April, he will order the destruction of Iran’s energy plants. The US president pushed back the deadline of a previous ultimatum that he had set for last Monday.

Israel targeted a range of sites associated with Iran’s nuclear programme on Friday, including a heavy-water plant and a yellowcake production plant, according to the official Iranian news agency. Yellowcake is a concentrated form of uranium after impurities are removed from the raw ore. Heavy water is used as a moderator in nuclear reactors.

Iran’s Atomic Energy Organisation said the Shahid Khondab heavy-water complex in Arak and the Ardakan yellowcake production plant in Yazd province were targeted, the agency said. The strikes did not cause any casualties and there was no risk of contamination, it said.

Other US and Israeli strikes continued to target Iran’s missile stockpile and launchers. Israel’s military said its attacks on Friday hit sites “in the heart of Tehran” where ballistic missiles and other weapons were produced. It said it also hit missile launchers and storage sites in western Iran.

Reuters reported that the US could only confirm that about a third of Iran’s missile arsenal had been destroyed, according to five people familiar with the US intelligence. One source said the intelligence on Iran’s drone capability was similar, with about a third probably destroyed.

Iranian missiles and drones strikes have continued at a roughly consistent level, with between 10 and 20 targeting Israel daily, which experts say does not suggest significant shortages. On Friday, attacks targeted the Saudi capital, Riyadh, and two major ports in Kuwait as Tehran gave no direct sign that it was ready for negotiation or compromise.

Casualties around the Middle East continue to mount. Eighteen people have died in Israel, while four Israeli soldiers have also been killed in Lebanon. Thirteen US military members have died, as well as civilians on land and sea in the Gulf region. In Iran, more than 1,900 people had been killed and at least 20,000 injured, said Maria Martinez of the International Federation of Red Cross and Red Crescent Societies. Others estimate lower numbers.

In Lebanon, the Israeli military operation in the south has displaced a fifth of Lebanon’s population, triggering a humanitarian crisis. Nearly 1,100 people in Lebanon have been killed in the Israeli offensive. It follows attacks on Israel by Hezbollah, the Iran-backed Islamist militant movement.

Both Israel and the US say they want to ensure that Iran can no longer threaten Israel with ballistic missiles or its nuclear programme, which Iran says is purely civilian, or through allied organisations, such as Hezbollah.

The more ambitious aim of regime change has been played down by officials in both countries in recent days. New data from ACLED, the independent global conflict monitor, shows there have been more than 850 pro-regime demonstrations and protests in Iran since the beginning of the war, which, experts said, suggested Iran’s leaders could still organise and mobilise large numbers of people despite significant losses.

There is little clarity over the exact status of any contacts between mediators such as Pakistan or Turkey and Iran and the US.

Rubio said Iran had sent “messages” but not a response to Washington’s 15-point proposal, which Pakistan passed on to Iran earlier this week.

The US proposal included demands ranging from the dismantling of Iran’s nuclear programme to the curbing of its missile development and effectively the handing over of control of the strait of Hormuz, according to sources and reports.

An Iranian official told Reuters on Thursday that senior Iranian officials had reviewed the proposal and felt it served only US and Israeli interests. But they said diplomacy had not ended.

On Thursday, Trump said that talks were continuing “despite erroneous statements to the contrary by the Fake News Media, and others” and were “going very well”.

In a joint statement, the G7 foreign ministers “reiterated the absolute necessity to permanently restore safe and toll-free freedom of navigation in the strait of Hormuz” and called for “an immediate cessation of attacks against civilians and civilian infrastructure”.

UK officials viewed the statement as having moved events on relatively little, with one saying: “The joint statement doesn’t say much, but there was speculation beforehand that we might not even get a joint statement at all – so it is something.”

US and other media reported an apparent deployment of mines by the US in southern Iran. Three experts told the Bellingcat investigative news website the munitions were air-delivered US-made Gator anti-tank mines.