EU piles last-minute pressure on US over Iran nuclear deal

"That is not changing," she said. She noted that the International Atomic Energy Agency (IAEA) had also confirmed the full compliance of the deal some ten times.

The statements comes ahead of a possible decision by US president Donald Trump on Tuesday to withdraw from the deal, ahead of a 12 May deadline on whether to re-certify it.

Trump had promised to tear up the agreement, signed by the Obama administration in 2015, during his campaign bid to become US president with belligerent statements that appear to cater to his populist voter base.

Trump at the time had described it as "worst deal ever negotiated", taking issue with, among other things, the so-called sunset clause that allows Iran to resume part of its nuclear programme post-2025.

The pact was brokered by the P5+1 – the five permanent members of the United Nations Security Council – the US, the UK, France, China, and Russia – plus Germany, with the European Union involved as well.

It meant easing economic sanctions on Iran. In exchange, Iran would scale down its nuclear programme.

Earlier this year in January Trump had waived sanctions on Iran but warned a new round could be imposed given Tehran's ballistic missile programme and claims it may still develop nuclear weapons.

Those sanctions target the Iranian central bank and penalise states that purchase Iranian oil exports.

Germany's foreign minister Heiko Maas, on Monday, said the deal needed to remain in place.

"We don't think there is any justifiable reason to pull out of this agreement and we continue to make the case for it to our American friends," he said.

Oil-rich nations like Norway could see a temporary spike in prices for the commodity should the US reinstate full sanctions.

The EU may also remain part of the deal, regardless of US involvement, in a move that Tehran on Monday suggested could be possible.

A US withdrawal may also complicate Trump's efforts to scrap North Korea's nuclear programme.