US President Donald Trump has said an Israeli strike on Iran "could very well happen," and a senior Israeli official told the Wall Street Journal it could occur as soon as Sunday unless Iran agrees to halt production of material for an atomic bomb.
This has raised fears that such a move could spark a regional war and retaliatory strikes from Iran.
Mr Trump reiterated his hopes for a peaceful end to the tensions.
"We remain committed to a Diplomatic Resolution to the Iran Nuclear Issue!" he wrote on his Truth Social platform.
"My entire Administration has been directed to negotiate with Iran. They could be a Great Country, but they first must completely give up hopes of obtaining a Nuclear Weapon," Mr Trump added.
Tensions have been building in the region as Mr Trump's efforts to reach a nuclear deal with Iran appear to be deadlocked.
US intelligence has indicated that Israel has been making preparations for a strike against Iran's nuclear facilities.
US and Iranian officials are scheduled to hold a sixth round of talks in Oman on Sunday about Iran's escalating uranium enrichment programme, according to officials from both countries and their Omani mediators.
Breach of non-proliferation obligations
Earlier, the UN nuclear watchdog's board of governors declared Iran in breach of its non-proliferation obligations, and Iran announced countermeasures.
A senior Iranian official said a "friendly country" had warned it of a potential Israeli attack.
Security concerns have risen since Mr Trump said yesterday that American personnel were being moved out of the region because "it could be a dangerous place" and that Iran would not be allowed to develop a nuclear weapon.
The US is concerned that Israel could take military action against Iran in the coming days, US officials said on condition of anonymity, despite Mr Trump's recent warning to Israeli Prime Minister Benjamin Netanyahu against such a strike while US diplomacy continues with Iran.
Mr Netanyahu raised the possibility of strikes in a phone conversation with Mr Trump on Monday, the Journal reported, citing two US officials.
"I don't want to say imminent, but it looks like it's something that could very well happen," Mr Trump told reporters at a White House event, adding Iran could not be allowed to develop a nuclear weapon.
"I'd love to avoid the conflict," he said. "Iran's going to have to negotiate a little bit tougher, meaning they're going to have to give us something they're not willing to give us right now."
Security in the Middle East has already been destabilised by spillover effects of Israel's war in Gaza.
Mr Trump has threatened to bomb Iran if the nuclear talks do not yield a deal and said he has become less confident Iran will agree to stop enriching uranium.
Iran wants a lifting of US sanctions imposed on it since 2018.
Earlier, Mr Trump expressed frustration that oil prices had risen amid supply concerns arising from potential conflict in the Middle East.
With the US offering little explanation for its security concerns, some foreign diplomats suggested that the evacuation of personnel and US officials anonymously raising the spectre of an Israeli attack could be a ploy to ratchet up pressure on Iran for concessions at the negotiating table.
A senior Iranian official told Reuters the latest tensions were intended to "influence Tehran to change its position about its nuclear rights" during the talks.
Iranian President Masoud Pezeshkian said that even if the country's nuclear facilities were destroyed by bombs, they would be rebuilt, state media reported.
The International Atomic Energy Agency's (IAEA) board of governors declared Iran in breach of its non-proliferation obligations for the first time in almost 20 years, raising the prospect of reporting it to the UN Security Council.
The step is the culmination of a series of stand-offs between the IAEA and Iran since Mr Trump pulled the US out of a nuclear deal between Iran and major powers in 2018 during his first term, after which that accord unravelled.
An IAEA official said Iran had responded to the 35-nation board's declaration by informing the UN watchdog that it plans to open a third uranium enrichment plant.
