Iran warned on Sunday that any renewed war with the United States could last longer than the previous round of fighting, after President Donald Trump said he still had to "take care" of more targets.

Diplomatic efforts to end the Middle East war have been punctuated by repeated threats from the US and Israel to resume bombardments as they hold crucial elections.

"A potential future war could last longer than previous conflict, and the American president would not be in a position to dictate the timing or the conditions of its conclusion," said army spokesman Mohammad Akraminia, according to Iranian state television.

In the most intense phase of the war, which began on February 28 with US-Israeli strikes on Iran, Tehran retaliated with missile and drone attacks across the region. Iran-aligned armed groups joined the fighting in Lebanon and Yemen.

Akraminia's remarks followed Trump's suggestion that the US could swiftly strike its remaining targets in Iran.

"We still have to take care of, I would say one or two sites, but we can do that in 10 minutes," Trump told reporters.

"You probably could look at Pickaxe Mountain, and you have to take care of that. We can do that all very quickly," he added, referring to a suspected underground nuclear complex.

US media reported that Trump had held a call with Israeli Prime Minister Benjamin Netanyahu on Saturday over whether and when to ramp up combat operations against Iran.

Axios quoted one US and one Israeli official saying the two leaders discussed the state of negotiations with the Islamic republic, with Netanyahu pressing the president to strike Iran immediately after Tuesday's US midterm elections and Trump eager to let negotiations play out.

The Israeli source described the call as "tough", while the US source said it was "direct", according to Axios.

Speaking to reporters on Sunday, Trump confirmed he had discussed Iran with Netanyahu, but would not elaborate.

'No geographical limitations'
Top military and political officials in Iran have warned against any new attack.

Revolutionary Guards spokesman Hossein Mohebbi on Sunday echoed a warning issued a day earlier in a written message by Iran's new supreme leader, Ayatollah Mojtaba Khamenei.

"In a conflict with America, there are no geographical limitations; a vast theatre has been defined for inflicting damage upon the enemy," Mohebbi said, according to state television.

Foreign Minister Abbas Araghchi said: "We hope the other side will exercise rationality and choose diplomacy," adding that Iran "remains prepared for both defence and diplomacy", according to the official IRNA news agency.

The warnings came as Iran's security chief Mohsen Rezaei disclosed on Saturday that he had received a letter from US Vice President JD Vance seeking to revive talks.

Rezaei noted what he described as a positive change in "tone" from the US side but said he had yet to respond.

He said Tehran had previously told Washington that unless its conditions were met, "neither would the Strait of Hormuz be reopened nor would there be any negotiations".

Those conditions include unfreezing Iranian assets abroad, ending the months-long US naval blockade of Iranian ports, lifting longstanding sanctions and ending the war on all fronts.

Since the war began, Iran has claimed control over the Strait of Hormuz, a vital global energy conduit, and repeatedly targeted vessels attempting to cross without its authorisation.

The US has imposed a naval counter-blockade on Iranian ports.

'Braced for the worst'
Anwar Gargash, diplomatic adviser to the Emirati president, said on Sunday that the United Arab Emirates hoped the exchanges would yield a breakthrough but was preparing for the worst.

"We're hoping that there is a diplomatic breakthrough," he told a conference in Manama.

"It is not the interest of the region to go through another round... But I think we're also, as we've shown before, braced for the worst."

In Tehran, some residents described a sense of helplessness as threats of renewed fighting mount.

"The news coming in is truly worrying. However... there is nothing I can actually do about it," Mohadese, a 27-year-old health inspector, told AFP.

Others including 48-year-old vendor Ebrahim saw no reason to be concerned.

"We do not fear another war; we have been at war for 48 years now -- we are always at war," he said in downtown Tehran.