Trump to announce decision on Iran accord today

US President Donald Trump said that he would announce his decision on whether Washington will pull out of the Iran nuclear accord at 2 p.m. on Tuesday, media reports said.

"I will be announcing my decision on the Iran deal tomorrow from the White House," he tweeted on Monday afternoon.

Trump is weighing whether to continue waiving sanctions on Iran's energy and banking sector that were lifted as part of the 2015 agreement in exchange for curbs on Tehran's nuclear programme, reports CNN.

Tuesday's announcement will be the most consequential national security decision of Trump in the last 15 months since he took office as the US President. 

Trump excoriated the agreement - signed among Iran and the 5+1 Group consisting of the US, Russia, China, France, the UK and Germany - even before winning the 2016 election, as the "worst deal ever" and promised to tear it up on his first day in office.

One European diplomat said it seems fairly clear that the administration will walk away from the deal, and described the chances that the Joint Comprehensive Plan of Action, as the deal is formally known, will continue intact as "very small".

"It's pretty obvious to me that unless something changes in the next few days, I believe the President will not waive the sanctions," the diplomat told CNN. 

"And that will have various consequences that I think we have yet fully to understand and spell out."

The implications of a US departure from the agreement aren't clear yet, but analysts have warned that it would send a message to other nations, particularly North Korea, about the reliability of the US as a negotiating partner.

According to the deal, which was former President Barack Obama's signature foreign policy achievement, the West would end three decades of sanctions and isolation of Tehran that had crippled the country's economy and fueled domestic impatience with its clerical leaders, reports The New York Times. 

In return, Iran agreed to ship roughly 97 per cent of its nuclear fuel out of the country, and forgo production of nuclear fuel, even for ostensibly peaceful purposes.

In the 28 months since the arrangement went into effect, international inspectors have said they have found no violations - apart from minor infractions that were quickly rectified.

Under the deal, the restrictions on research and development in Iran's nuclear program would begin to lift after a decade. 

After 15 years, Iran would be able to produce as much fuel as it wanted - though never for the purpose of making weapons.

French President Emmanuel Macron, German Chancellor Angela Merkel and British Foreign Minister Boris Johnson have come to Washington in recent days to bring pressure to bear on Trump to keep the US in the accord.

Iranian President Hassan Rouhani has warned that the US will quickly regret it if it abandons the nuclear accord, at the same time that he reiterated his opposition to negotiating a new pact.