US Ambassador to the UN, Nikki Haley addresses the Security Council at UN headquarters in New York, July 5, 2017.

:: The head of the UN’s atomic watchdog met US President Donald Trump’s UN envoy Nikki Haley on Wednesday to brief her on the 2015 Iran nuclear deal, as concerns grow about the accord’s future.

Reports by the Vienna-based International Atomic Energy Agency (IAEA) have shown Iran to be in compliance with its landmark agreement with six major powers.

The deal saw Iran shrink its atomic activities and submit to closer IAEA inspections in order to make any dash to make a nuclear bomb extremely difficult.

Most UN and Western sanctions on Iran were lifted in return, but others related to non-nuclear issues have remained in place or been ratcheted up.

With Trump slamming the “terrible” 2015 deal, tensions have risen between the two long-time foes, with both accusing each other of not adhering to the “spirit” of the accord.

President Hassan Rouhani said last week that Iran could walk away within hours, accusing Washington of “constant and repetitive breaking of its promises” under the deal.

Haley responded that the new sanctions are related to Iran’s support for “worldwide terrorism” and other behavior, and that Iran cannot “use the nuclear deal to hold the world hostage”.

Trump is due in October to certify to Congress whether Iran is sticking to the deal.

In July he told the Wall Street Journal he “would be surprised if they were in compliance”.

Haley made no comment to reporters on Wednesday as she arrived for her talks with IAEA chief Yukiya Amano.

The Washington Post on Tuesday quoted her as saying her talks were to answer US questions about the watchdog’s inspections and monitoring.

“We have no decision made” about whether to scrap the deal, Haley was quoted as saying.

“What we are doing is trying to find out as much information as we can.”

“The Trump administration needs a wake-up call on the costs of sabotaging the nuclear deal with Iran,” Arms Control Association analyst Kelsey Davenport told AFP.

“Hopefully visiting the IAEA will allay concerns about monitoring the agreement and demonstrate to Haley that the deal put Iran’s nuclear program under a microscope and keeping it there is the best way to guard against any illicit nuclear activity,” Davenport said.