US, EU at odds over uncertain Iran deal

"Congress is likely to re-impose sanctions, but if it doesn't, President Trump is likely to abrogate the nuclear agreement himself," Phillips said.

The deal, clinched in July 2015 between Iran and the six countries of Britain, China, France Russia and the United States, plus Germany, after a decade of negotiations, has seen Iran scale down nuclear projects in exchange for international sanctions easing.

Others do not necessarily forecast the death of the deal, but say there is much uncertainty on the horizon.

"The Iran deal is suffering a lot of duress right now. It is not clear how Trump will handle it because he has delegated the issue to Congress to handle," Brookings Institution Senior Fellow Darrell West told Xinhua.

"They could seek to impose new conditions, which would be very problematic for the European Union and Iran. Or legislators may be unable to agree, which could end up preserving the status quo," West said.

"For right now, it looks like there will be lots of uncertainty for a few months," West said.

Meanwhile, Thursday saw what experts said could become a war of words between the White House and Iran, as the Islamic Republic's Ayatollah in a speech called Trump "foul mouthed" and accused him a "pretending to be an idiot."

Experts said this may be the opening salvo of a war of words with Trump, as the US president is known to make impetuous, off-the-cuff remarks, especially via social media platform Twitter.

Phillips said: "I think US-Iran tensions are rising regardless of what happens with the nuclear deal."