North America

US weighs staying in Iran nuclear deal

Donald Trump isn't even telling his top advisers what his decision on the Iran nuclear deal is.

President Donald Trump has determined how he wants to approach the Iran nuclear deal - which he has called the worst agreement ever negotiated by the US - but hasn't told even his top national security advisers what his decision is.

Secretary of State Rex Tillerson said on Wednesday that Trump had not informed him or others in the administration about his decision and had refused to share it with British Prime Minister Theresa May when she asked him about it.

Tillerson said he had been surprised when Trump publicly announced he had reached a decision. The secretary told reporters it would now take some time to prepare to implement the decisions.

He gave no hint as to the direction Trump would take, but repeated the president's long-standing position that the deal does not address troubling non-nuclear behaviour despite the hopes of those who negotiated it.

Tillerson spoke to reporters after a meeting of the parties to the nuclear deal, including Iranian Foreign Minister Mohammad Javad Zarif. The meeting marked the highest-level US-Iranian encounter since Trump became president.

European Union foreign policy chief Federica Mogherini, who hosted the meeting, said all parties to the accord - including Tillerson - agreed it "is working and is delivering for its purpose."

Tillerson did not dispute Mogherini's characterisation but said that while Iran might be meeting its obligations to the letter of the deal, it is violating its spirit.

"Perhaps the technical aspects have (been met), but in the broader context the aspiration has not," Tillerson said.

However, he said the Trump administration was determined to address the flaws in the deal, the most serious of which are so-called "sunset provisions" that allow Iran to resume some aspects of its nuclear program after certain periods of time.

The meeting in the UN Security Council chambers followed two days of increasingly hostile rhetoric between Trump and Iranian President Hassan Rouhani, as well as Trump's surprise announcement about a decision on the nuclear deal.