The United States is "accelerating" its attacks on Iran, US Defense Secretary Pete Hegseth has said, while US President Donald Trump claims Iranian officials have tried to "make a deal".
The war, now in its seventh day, has seen European countries increase the deployment of military assets to the Middle East and has left world leaders bracing for the impact on the global economy.
Speaking at a press briefing on Thursday, local time, Mr Hegseth said while the US was not expanding its military objectives in Iran, its operations were "advancing decisively".
"The amount of firepower over Iran and over Tehran is about to surge dramatically," he said.
He also said the UK's decision to let the US use its military bases was helping the US ramp up its campaign.
"It's unfortunate that the Brits, from day one, didn't say, 'Hey, go ahead and have access,'" he said.
"But we got there."
The comments came as the US president reportedly said he needed to be personally involved in the selection of Iran's next leader.
Speaking at the White House, Mr Trump also claimed Iran's missile and drone capabilities had been destroyed, and that Iranian officials had called him to try and negotiate a deal.
"They're tough and they want to fight," he said.
"They're calling, they're saying, 'How do we make a deal?' I said, 'You're being a little bit late.'
"We want to fight now more than they do."
But Iranian Foreign Minister Abbas Araghchi said Iran had refused any negotiations with the US and had not asked for a ceasefire.
Speaking to NBC News, Mr Araghchi struck a defiant tone warning Iran was prepared for a possible ground invasion by American troops — action the US is yet to rule out.
"No, we are waiting for them … because we are confident that we can confront them, and that would be a big disaster for them," he said.
Israel threatens to 'bring hell' to Lebanon
Israel meanwhile has threatened further strikes in Lebanon, pulling its northern neighbour deeper into the widening conflict.
Earlier, the Israeli military warned residents to leave parts of the Lebanese capital, triggering a panicked exodus and traffic chaos across the densely populated city of Beirut.
Lebanon was drawn into the conflict earlier this week when the Iran-backed Lebanese militia Hezbollah fired rockets into northern Israel, prompting Israeli air strikes targeting the southern suburbs of Beirut as well as parts of southern and eastern Lebanon.
Israeli Finance Minister Bezalel Smotrich posted a video on X warning Dahiyeh, a suburb in the south of Beirut, would soon resemble parts of Gaza.
"You wanted to bring hell on us, but you have brought hell upon yourselves. The Dahiyeh will look like Khan Younis," Mr Smotrich said, who sits on Prime Minister Benjamin Netanyahu's security cabinet.
While Israel has previously ordered people to leave buildings in Dahiyeh, it is the first time it has instructed residents of the entire area to leave, prompting hundreds of displaced people to gather in downtown Beirut.
At least 102 people have been killed in Israeli attacks since Monday, according to the Lebanese health ministry.
France announced it will strengthen its cooperation with the Lebanese Armed Forces and provide armoured transport vehicles as well as operational and logistical support.
"Everything must be done to prevent this country, so close to France, from once again being drawn into war," French President Emmanuel Macron said on X.
A fresh wave of attacks
Israel has continued to pound Tehran with a new wave of strikes over the Iranian capital.
In the United Arab Emirates, the defence ministry has reported more Iranian missile and drone threats, while explosions have been reported in Qatar, Kuwait and Bahrain.
Iran has also launched a salvo of missiles at Israel and allegedly sent drones into Azerbaijan, injuring four people in the Nakhchivan exclave located to Iran's north.
Iran's armed forces denied firing the drone at its northern neighbour and blamed the action on Israel.
Azerbaijan President Ilham Aliyev vowed to retaliate against Iran, raising concerns about further spillover from the conflict.
"We will not tolerate this unprovoked act of terror and aggression against Azerbaijan," he said.
"Our armed forces have been instructed to prepare and implement appropriate retaliatory measures."
Iran has also vowed to take revenge for a US torpedo attack on an Iranian warship off the coast of Sri Lanka, which killed more than 80 sailors.
Mr Araghchi said Washington would "bitterly regret" the precedent it had set by sinking a ship in international waters without warning.
Sri Lanka has recovered scores of bodies and its navy rescued 32 people, with 11 people yet to be accounted for.
The Australian federal government could not confirm whether Australian personnel were on board the American submarine, after reports that two Australian sailors were on board.
Nine oil tankers have now come under attack in Gulf waters since the conflict broke out at the weekend.
This includes a Bahamas-flagged crude oil tanker that was targeted by an Iranian remote-controlled boat laden with explosives while anchored near an Iraqi port.
A second tanker anchored off Kuwait was taking on water and spilling oil after a large explosion on its port side.
Trump demands say in Iran's next leader
Inside Iran, the body of supreme leader Ayatollah Ali Khamenei, who was assassinated in the first hours of the US–Israeli air campaign, had been due to lie in state in a prayer hall in the nation's capital, Tehran.
The event was set to draw thousands of mourners and mark the beginning of three days of mourning across the country for the leader who ruled Iran for 36 years.
But the memorial was abruptly and indefinitely postponed shortly before it was due to begin.
In the hours before announcing the delay, Iranian officials had said they were close to naming Khamenei's hardline son, Mojtaba, as his successor in what would be a strong gesture of defiance.
Mojtaba Khamenei, a mid-ranking cleric with close ties to Iran's elite Revolutionary Guards, is one of the most influential figures in the Iranian clerical establishment.
Earlier, Mr Trump reportedly told Axios he needed to be personally involved in selecting Iran's next leader.
"Khamenei's son is unacceptable to me. We want someone that will bring harmony and peace to Iran," Mr Trump told Axios.
Iranian officials gave no reason for the postponement of the memorial, but Reuters has reported the delay was motivated in part by fears of assassination among those attending while Israeli and US warplanes remain in the skies.
The escalation comes as the US House of Representatives has rejected an effort to stop Mr Trump's war on Iran and require any hostilities against Iran be authorised by Congress.
It is the second vote to fail in as many days after the bid failed in the Senate, granting the president free rein to conduct his military campaign.
Iran's attacks on the Persian Gulf's energy sector have pushed crude oil prices up by more than $US10 a barrel, posing a major challenge to affordability concerns and other domestic issues in the US ahead of fast-approaching midterm elections.
ABC/wires
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