The EU's top diplomat Federica Mogherini said Friday that the Iran nuclear deal was "working and delivering", insisting US President Donald Trump did not have the power to terminate it.
Mogherini, who was touted as a Nobel Peace Prize candidate for her work on the 2015 agreement, said the EU would abide by it and she expected other parties to do the same.
"We cannot afford as an international community, as Europe for sure, to dismantle an agreement that is working and delivering," she said after Trump announced he would not certify the agreement, and warned he may yet walk away from it.
Trump stopped short of withdrawing from the deal to curb Iran's nuclear programme but said it would be under continuous review and he could pull out "at any time".
Mogherini stressed, however, that the accord reached between Iran and Britain, China, France, Germany, Russia and the United States after 12 years of bargaining, "does not belong to any single country".
"To my knowledge there's not one single country in the world that can terminate a UN security council resolution that has been adopted, and adopted unanimously, and implemented, and verified," she said.
"It is clearly not in the hands of any president of any country in the world to terminate an agreement of this sort. The president of the United States has many powers (but) not this one."
Both the US government and UN nuclear inspectors say Iran is meeting the technical requirements of its side of the bargain, dramatically curtailing its nuclear programme in exchange for sanctions relief.
But Trump said the agreement had failed to address Iranian action in the Middle East and its missile programme, adding that he would support efforts in the US Congress to work on new measures to address these issues without sinking the deal.