US officials said Thursday the US had waived nuclear sanctions only grudgingly. "The administration did approve waivers in order to maintain some flexibility," State Department spokeswoman Heather Nauert said.

A senior administration official, speaking on condition of anonymity, told the French news agency Agence France-Presse the waiver was "a holding action."

"This is the action that the US is taking in the interim, while the president and his cabinet come to a final decision in consultation among themselves and in consultation with allies," he said.

Read more: Iran threatens to quit nuclear deal

The 2015 deal — approved by Trump's predecessor Barack Obama — was implemented under a Joint Comprehensive Plan of Action (JCPOA) and enshrined in UN Security Council Resolution 2231. Under the JCPOA, Iran surrendered much of its enriched uranium, dismantled a reactor and submitted nuclear sites to UN inspection, while Washington and Europe lifted some sanctions.

The International Atomic Energy Agency (IAEA) has reported that Iran has lived up to the terms of the nuclear agreement.

But Tehran has continued to develop and test ballistic missile technology banned under previous UN resolutions, and its Revolutionary Guard Corps supports militias in Syria, Iraq, Lebanon and Yemen.

On Thursday, the US Treasury imposed economic sanctions on 11 individuals and companies accused of supporting Iran's Revolutionary Guards or engaging in cyberattacks against US banks, targeting an engineering company, two air transport firms and an IT company. 

Read more: From Russia to Syria and Iran: Do EU sanctions really work?

Trump blasts

"You'll see what I'm going to be doing very shortly in October," Trump told reporters. "The Iran deal is one of the worst deals I've ever seen. Certainly at a minimum the spirit of the deal is atrociously kept. The Iran deal is not a fair deal to this country. It's a deal that should not have ever been made."

US Secretary of State Rex Tillerson said Thursday that Trump would "take into account the totality of Iranian threats, not just Iran's nuclear capabilities. In our view, Iran is clearly in default of these expectations," he said.

Tillerson said Iran continues to support Bashar al-Assad's brutal regime in Syria, to develop ballistic missiles and to carry out cyberattacks, threatening Middle East security.

Critics fear the worst

Some believe a decision to scrap the deal could alienate other interested parties — Britain, China, France, Germany and Russia — and allow Iran to resume its quest for a nuclear weapon. It could also in turn undermine US credibility in relation to North Korea.

Colin Kahl, a former Obama administration national security official, told Agence France-Presse Iran could have enough enriched fuel for a bomb within a year of the deal collapsing, dubbing the Trump policy a "train wreck."

"You won't have a diplomatic option because in the event that we get blamed for blowing up the deal we won't be able to reconstitute international consensus," he said.

jbh/cmk (AFP, AP)