Donald Trump says he won't recertify a deal designed to stop Iran getting nuclear weapons.
It was set up in 2015 by Barack Obama and other international leaders - and independent observers believe it's working.
However, President Trump claims the deal - which he has repeatedly criticised and described as 'one of the worst' - is too lenient.
Mr Trump says he'll refer the deal to Congress - calling Iran a "fanatical regime" which is supporting terror.
He blamed Iran for spreading "death, destruction and chaos all around the world", claiming the regime had committed multiple infringements of the international deal.
He added that "the agreement will be terminated" if a solution cannot be found by working with Congress and US allies.
He stated: "It is time for the entire world to join us in demanding that Iran’s government end its pursuit of death and destruction."