Donald Trump has refused to say whether the US will order strikes on Iran, warning Tehran "nobody knows what I'm going to do".
The US president spoke to reporters outside the White House after Iran's supreme leader, Ayatollah Ali Khamenei, rejected Washington's demand for "unconditional surrender" and warned a US intervention in the conflict with Israel would lead to "irreparable harm".
Airstrikes between Iran and Israel look set to enter a seventh day on Friday, with little sign of either side backing down.
On Wednesday, Mr Trump said that his patience had "run out" but declined to say whether the US would join in Israeli strikes.
"I may do it. I may not do it. I mean, nobody knows what I'm going to do," he said, when asked directly if US forces would be involved.
He said Iranian officials had reached out about negotiations, including a possible meeting at the White House, but added it was "very late to be talking".
Asked for his response to Mr Khamenei defying the US's demand for surrender, Mr Trump said: "I say, good luck."
"Unconditional surrender, that means I've had it," he added.
A source familiar with internal discussions said Mr Trump and his team were considering options that included joining Israel in strikes against Iranian nuclear installations.
Defense Secretary Pete Hegseth told a Senate committee on Wednesday that the Pentagon was prepared to execute any order given by the president.
Israeli prime minister praises Trump
At a later press conference, Mr Trump repeated that he was yet to make a decision on whether to attack Iran, and said a change in Iran's government "could happen".
But the US president also kept the door open for a deal with the Islamic republic, noting that many of his domestic supporters "don't want to see Iran get a nuclear weapon".
Meanwhile, Israeli Prime Minister Benjamin Netanyahu, in a video released by his office on Wednesday evening, said Israel was "progressing step by step" towards eliminating threats posed by Iran's nuclear sites and ballistic missile arsenal.
"We control the skies over Tehran. We are striking with tremendous force at the regime of the ayatollahs. We are hitting the nuclear sites, the missiles, the headquarters, the symbols of the regime," Mr Netanyahu said.
He also thanked Mr Trump, "a great friend of the state of Israel", for standing by its side in the conflict, saying the two were in continuous contact.
'The people of Iran do not surrender'
In a televised address, Mr Khamenei was defiant and said Iranians were standing "firm against an imposed war".
"The people of Iran do not surrender to any kind of imposition," he said.
The ayatollah also warned against American involvement, saying it would "eventuate in a worse outcome for America".
"The entry of America in this matter, the entry of America's military in this matter would cause irreversible damage to itself and it will have a greater impact on that nation than on Iran."
Iran's mission to the United Nations also responded to Mr Trump in posts on X: "Iran does NOT negotiate under duress, shall NOT accept peace under duress, and certainly NOT with a has-been warmonger clinging to relevance," it wrote.
Israeli strikes continued to hit the Iranian capital Tehran on Wednesday, with smoke seen billowing over the city's skyline.
Israel's Defence Minister Israel Katz said Iran's police headquarters was among the targets struck, while the Iranian Red Cross said a strike hit near its own building in Tehran.
"As we promised — we will continue to strike at symbols of governance and hit the ayatollah regime wherever it may be," Mr Katz said.
Iranian officials have not issued updated casualty figures since Sunday, when they said 224 people had been killed by Israel's military strikes.
Tehran's ballistic strikes have so far killed 24 people in Israel.
Meanwhile, Iranians jammed the highways out of the capital Tehran, fleeing from intensified Israeli airstrikes.
Since Friday, Iran has fired around 400 missiles at Israel, some 40 of which have pierced through air defences, killing 24 people, all of them civilians, according to Israeli authorities.
In Israel, Iran's missile volleys mark the first time in decades of shadow war and proxy conflict that a significant number of projectiles fired from Iran have penetrated defences, killing Israelis in their homes.
With Mr Khamenei's main military and security advisers killed, the leader's inner circle has been narrowed, raising the risk that he could make strategic errors, according to five people familiar with his decision-making process.
Israelis seek to leave
Meanwhile, the threat of Iranian strikes left Israel's largest city, Tel Aviv, uncharacteristically quiet.
Usually choked with traffic and buzzing with activity, residents had either fled to other parts of Israel or were staying at home close to shelters should missile alerts ring out.
With the country's main airport still closed and land border crossings clogged, some have boarded chartered boats in the marina in Herzliya to leave the country.
Miam resident Pauline Markowicz had been staying in Herzliya, before deciding to leave the country.
A missile hit not far from where she was sheltering on Tuesday morning.
"I was supposed to leave yesterday — I got injured, I need surgery, I can't get it done because it's not important enough in the time of war," she told the ABC, her arm in a sling.
"So this is really the best way to leave.
"I could have left through Jordan or Egypt, but it's a long way — it's not as safe, so this is my way to try and go home and get back to life."
While many foreigners cross land borders in and out of Israel, it is less common for Israelis to do so.
Prices ranged from around 1,000 shekels ($440) for a chartered voyage taking more than 20 hours, to more than 10,000 shekels ($4,600) for a fast boat to Cyprus.
"I feel bad abandoning and leaving but I have to — you know, some people have to go," passenger Roy Rankin said, who was hoping to get back to the United States.
"They look for the best option for them, this seems to be the best one for me."
One of the boat charters usually operates as a sailing school.
"12 boats we have in our company, and we are going around the clock," Captain Avi Moysa told the ABC.
"It's a kind of madness about it — there is a lot of people that are stuck in Cyprus and there was a lot people that they want to go out from Israel to Cyprus, out anywhere.
"This is the only way now, these days it's the only to go out from Israel."
Iran bans filming
Inside Iran, authorities are intent on preventing panic and shortages.
Fewer images of destruction have been allowed to circulate than in the early days of the bombing, when state media showed pictures of explosions, fires and flattened apartments. A ban on filming by the public has been imposed.
The state has placed limits on how much fuel can be purchased. Oil Minister Mohsen Paknejad told state TV that restrictions were in place to prevent shortages, but there would be no problem supplying fuel to the public.
A London-based online watchdog, Netblocks, on Wednesday also said Iran was experiencing a "near-total internet blackout".
Trump rejects Putin's mediation offer
Meanwhile, the US president has pushed back on his Russian counterpart's offer to mediate an end to the conflict.
With his own army busy in Ukraine, Vladimir Putin has in recent days put himself forward as the person to negotiate an end to hostilities between Israel and Iran.
But on Wednesday, Mr Trump appeared to rebuff that offer.
"He actually offered to help mediate, I said 'do me a favour, mediate your own. Let's mediate Russia first, okay?'" Trump told reporters at the White House.
"I said 'Vladimir, let's mediate Russia first, you can worry about this later.'"
Wealthy Gulf states such as Saudi Arabia and the United Arab Emirates (UAE) have also been involved in frantic diplomacy in recent days, fearing the conflict could spill across borders.
The UAE's Foreign Minister Sheikh Abdullah bin Zayed Al Nahyan said the Gulf country's president had "conducted intensive diplomatic calls … to de-escalate tensions and prevent the conflict from spreading".
British Prime Minister Keir Starmer also convened an emergency meeting of senior government officials to discuss the conflict and the possibility of US involvement.
ABC/wires
