Trump 'will withdraw from Iran deal', say officials

US President Donald Trump will announce that he is withdrawing from the landmark Iran nuclear deal, officials and diplomats have said.

Trump will confirm later on Tuesday whether he will make good on his threats to re-impose US sanctions on Tehran and thereby throw the entire deal into question.

Israeli Intelligence Minister Yisrael Katz said on Tuesday that Trump will throw out the 2015 deal, according to Israeli news website Arutz Sheva.

"The right way for President Trump to promote his policy and stop Iran is to announce the cancellation of the nuclear agreement and the return of economic sanctions on Iran," Katz said.

The former US ambassador to Israel, Dan Shapiro, made the same prediction.

"[Trump] will pull out, and Iran's & Euros' first reaction will be that the deal remains in place," Shapiro said on Twitter.

European diplomats told  The New York Times in a report published on Monday that the chances of Trump keeping the agreement intact was "very small."

The president has tweeted he will announce his decision at 2pm (6pm GMT), even as UK Foreign Secretary Boris Johnson shuttled around Washington trying to reach a last-gasp breakthrough.

Trump has unsuccessfully demanded changes to the Obama-era deal, which saw Iran mothball a suspected nuclear weapons programme in return for massive sanctions relief.

Months of intensive talks between the US and European allies now appear deadlocked, with Berlin, London and Paris refusing to rewrite the agreement.

Trump's decision to scrap sanctions relief would have global ramifications, straining Iran's already crisis-racked economy, heightening tensions in the Middle East and laying bare the biggest transatlantic rift since the Iraq War.

Tehran has sent mixed signals about its potential response, hinting it could leave a fatally undermined deal and return to military scale uranium enrichment.

Iran's President Hassan Rouhani said his country would stay in the agreement even if the US pulls out, but it is unclear whether Iran's more hardline military leaders, or Supreme Leader Ali Khamenei, hold the same view.