Washington DC - The US authorized the departure of non-emergency embassy staff from Israel on Friday as it threatened strikes on Iran and pressed its biggest military build-up in the Middle East in decades.

The move came a day after a round of Oman-mediated talks seen as a last-ditch bid to avert war, though initial optimism was tempered by Iran warning the US must drop "excessive demands" to reach a deal.

The world's largest aircraft carrier, the USS Gerald R. Ford, was due to arrive off the coast of Israel, in the latest aggressive move made by President Donald Trump. The US embassy in the country announced it was allowing non-emergency government personnel and family members to leave "due to safety risks".

"Persons may wish to consider leaving Israel while commercial flights are available," the embassy said on its website.

The New York Times reported that US Ambassador to Israel Mike Huckabee sent an email to embassy staff on Friday morning saying that those wishing to leave "should do so TODAY."

"Focus on getting a seat to anyplace from which you can then continue travel to DC, but the first priority will be getting expeditiously out of country," he was quoted as writing.

Growing concerns over conflict spurred China on Friday to join other countries in warning its citizens to leave Iran "as soon as possible."

Trump on February 19 gave Iran 15 days to reach a deal. While Iran has insisted the discussions focus solely on nuclear issues, the US and Israel want Tehran's missile program and its support for militant groups curtailed.

The Wall Street Journal reported on Thursday that Trump's negotiating team would demand that Iran dismantle its three main nuclear sites and hand over all its remaining enriched uranium to the US.

Without specifying what demands he was referring to, Iran's Foreign Minister Abbas Araghchi said on Friday that "success in this path requires seriousness and realism from the other side and avoidance of any miscalculation and excessive demands."

Following the talks in Geneva on Thursday, Araghchi told state TV that the negotiations "made very good progress and entered into the elements of an agreement very seriously, both in the nuclear field and in the sanctions field."

He said the next round would take place in "perhaps less than a week." with technical talks at the UN's nuclear agency to begin in Vienna on Monday.

Omani Foreign Minister Badr Albusaidi also announced technical discussions were to be held next week in Vienna.

"We have finished the day after significant progress," he said in a post on X.

UN nuclear chief Rafael Grossi joined the negotiations, a source close to the talks told AFP.

Trump said in his State of the Union address this week that Iran was "working to build missiles that will soon reach the United States of America," without offering any evidence for his claims.

He also accused Iran of "pursuing sinister nuclear ambitions," though Tehran has always insisted its program is for civilian purposes and categorically denied it was seeking to develop nuclear weapons.

The accusations were delivered in the same forum in which then-president George W. Bush laid out the case for the illegal invasion of Iraq in 2003.

The Iranian foreign ministry called these claims "big lies."