The United States cannot unilaterally terminate a 2015 nuclear deal between Iran and world powers, Federica Mogherini, the foreign policy chief of the European Union, has said, Haaretz reported.

Mogherini made the comments on Friday, just minutes after US President Donald Trump announced his decision not to certify the landmark accord.

"We cannot afford as the international community to dismantle a nuclear agreement that is working," said Mogherini, who chaired the final stages of the landmark talks. 

"This deal is not a bilateral agreement ... The international community, and the European Union with it, has clearly indicated that the deal is, and will, continue to be in place," Mogherini told reporters. 

"The president of the United States has many powers, but not this one," she added.

"The international community, and the European Union with it, has clearly indicated that the deal is, and will, continue to be in place."

Mogherini said she spoke to Rex Tillerson, the US secretary of state, immediately after Trump's speech on Friday.