International negotiations in Vienna mark the “last opportunity” for Iran to revive its original nuclear deal, the Foreign Secretary has warned.

Liz Truss told a joint press briefing, held alongside Israel’s foreign affairs minister, Yair Lapid, that Britain will “work flat out to prevent the Iranian regime from gaining nuclear weapons” and that “all options are on the table” if the discussions fail.

It came as indirect talks to resuscitate Iran’s 2015 nuclear deal, meant to prevent Tehran from developing nuclear weapons, began in the Austrian capital.

Ms Truss told reporters at a Foreign Office press conference: “We are absolutely determined to prevent Iran from securing a nuclear weapon, and all options are on the table.

“Talks are starting in Vienna today. We want Iran to agree to the original JCPOA (Joint Comprehensive Plan of Action, known as the Iran nuclear deal) – that is very important.

“And we want those talks to work. But if they don’t work, all options are on the table.”

Iran has ramped up its uranium enrichment since the US, under former president Donald Trump’s leadership, withdrew from the landmark nuclear agreement between world powers and Iran in 2018.

Cabinet minister Ms Truss said “we are now in a very difficult position” with regard to the situation with Tehran.

“We have seen the Iranians extending their capability towards acquisition of a nuclear weapon, so, as far as I’m concerned, these talks are the last opportunity for the Iranians to come to the table and agree the JCPOA agreement,” she added.

Foreign Secretary Liz Truss and Israeli Foreign Minister, Yair Lapid hold a news conference after a bilateral meeting at the Foreign Office
Foreign Secretary Liz Truss and Israeli foreign minister Yair Lapid held talks at the Foreign Office (Stefan Rousseau/PA)

Mr Lapid, meanwhile, urged the international community not to be persuaded to release sanctions on Iran, arguing that any economic boost would be used to “fund terror”.

The US has offered to lift some sanctions in exchange for Iran returning to full compliance with its nuclear commitments.

Asked whether Israel could back an interim deal if the current round of talks is unsuccessful, Mr Lapid said: “I would say no-one understands what an interim deal means but everyone understands the price of such a so-called deal, which is lifting sanctions.

“And lifting sanctions is money for the wrong people to be used for the wrong reasons. It is money to fund terror and to fund nuclear capabilities, and therefore we believe an interim deal is basically the wrong idea.

“We don’t know or not if there is the possibility to go back to the JCPOA.

“We do understand that the Iranians are going to lie their way through this and the world needs firm leadership in order to prevent them from becoming a nuclear power.”

Foreign Secretary Liz Truss and Israeli Foreign Minister, Yair Lapid signed a Memorandum of Understanding after a bilateral meeting at the Foreign Office
Foreign Secretary Liz Truss and Israeli foreign minister Yair Lapid signed a ‘memorandum of understanding’ (Stefan Rousseau/PA)

Downing Street said Iran would be responsible for the collapse of the JCPOA if an agreement is not reached in Vienna.

Prime Minister Boris Johnson’s official spokesman said the way Iran has “advanced” its nuclear programme is “undermining international security”.

The No 10 spokesman added: “If a deal is not swiftly concluded and Iran continues its nuclear escalation then they will be responsible for the collapse of the nuclear deal and a missed opportunity.”

The comments came after the Foreign Secretary and Mr Lapid – who is due to take over as Israel’s prime minister in 2023 – signed a “memorandum of understanding” in London on Monday, aimed at creating stronger collaboration on issues such as cybersecurity, defence and trade.

Mr Lapid said it is “possible” that current Israeli prime minister Naftali Bennett could sign a UK-Israel trade deal before the handover of power in Tel Aviv takes place, as he urged both countries to be “quick on our feet”.

He told the PA news agency: “I wish that we will sign this as quickly as possible. Let me tell you one thing on behalf of both of our governments – we mean business.”