Iran's supreme leader on Sunday warned the United States and Israel of fresh attacks following their threats to resume their strikes after crucial elections, as fears increased over a return to fighting.
US President Donald Trump has suggested he could launch fresh military action after the United States holds its midterm elections early next week.
But US Secretary of State Marco Rubio said on Sunday: "If there is a diplomatic solution, we would be open to it."
In Israel, which is coming off a general election, Prime Minister Benjamin Netanyahu has spoken of a "historic, one-time opportunity" to topple the Iranian government.
The elections in both countries could determine the direction of the conflict, with Israel having voted on Tuesday but yet to form a new government.
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"Any level or type of threat must be met with an immediate, impactful and geographically unrestricted response," Iran's supreme leader Mojtaba Khamenei told top military commanders, according to a statement.
Khamenei also ordered commanders to update Iran's target list to include "all types of tangible and intangible assets belonging to the American-Zionist enemy".
Iran has previously warned it would consider severing undersea cables in the Strait of Hormuz.
This was the first reported meeting between Khamenei and military top brass.
The supreme leader has not been seen publicly since before he took the helm in March, after the killing of his father, Ayatollah Ali Khamenei, in US-Israeli strikes.
Rubio warned that "we can achieve military objectives if we seek to", adding that Trump had not made a decision on any fresh strikes.
Since the initial US-Israeli bombardment in February, ordinary Iranians "have been left in a state of limbo for the past year", Fariba, an Iranian housewife, told the Agence France-Presse news agency.
But other residents in the Iranian capital brushed off the possible return to full-scale conflict.
"We do not fear another war," said Ebrahim, a salesman in his forties. "We have been at war for 48 years now."
Since the outbreak of the war, Iran has restricted shipping through the Strait of Hormuz, which normally carries around one-fifth of global oil consumption.
A ship traversing the strait struck a mine and caught fire, Iranian state television reported Saturday.
On Friday, Iran's Revolutionary Guards said three oil tankers had been halted after encountering unspecified "incidents" or hitting mines.
The blockade has caused a spike in global energy prices, making the war unpopular among the US public ahead of midterm congressional elections this week.
Gains for the opposition Democrats could restrict, to an extent, Trump's ability to enact policy.
Voting in Israel has left Netanyahu's political camp with the most seats in parliament but short of a majority, leaving the make-up of the next administration unclear.
The war began on 28 February with US-Israeli strikes on Iran. The Islamic republic swiftly responded with attacks on American assets in countries around the region.
Fresh diplomatic efforts are underway to avert any resumption of fighting.
Qatari mediators landed in Tehran on Friday, and US Vice President JD Vance sent a letter to Iran's security chief Mohsen Rezaei.
"I read the letter," said Rezaei, head of Iran's supreme national security council, in a video broadcast on Iranian television.
"I haven't yet responded. Their tone has completely changed", he added, describing that as "a good sign".
But he declined to comment further on its contents.
Iranian Foreign Minister Abbas Araghchi said there were currently no plans for meetings with US officials.
"Iran's conditions are clear, and consultations regarding them are ongoing among mediators," he said in an interview with Al Jazeera, according to the state news agency IRNA.
Rezaei insisted Iran would continue to blockade the Strait of Hormuz until its conditions, including releasing frozen assets, were met.
"We want the war to end in such a way that no one dares to attack Iran anymore," he added.
Qatar and Pakistan have been mediating between the warring parties, but the talks have yet to produce a lasting agreement.
The Wall Street Journal reported on Wednesday that Vance had sent his letter to Iran's security chief at Trump's direction to try to revive negotiations and avert further US strikes.
The Iranian side kept firm in its warnings against further attacks Saturday.
Army spokesman Mohammad Akaraminia said any resumption of hostilities would only expand the scope of the war.
"The flames of war will undoubtedly engulf a much wider geographical area," he said on social media.
Araghchi warned on X there would no longer be any "red lines".
