"We will not be the first to violate the accord but they should definitely know that they will regret it if they violate it," Rouhani told a conference to mark National Nuclear Technology Day in Tehran.

"We are much more prepared than they think, and they will see that if they violate this accord, within a week, less than a week, they will see the result."

US President Donald Trump has threatened to walk away from the nuclear deal and reimpose sanctions by May 12 unless tough new restrictions are imposed on Iran's nuclear and missile programmes.

Rouhani dismissed the threat, saying: "It's been 15 months since this gentleman who came to power in America has been making claims and there have been many ups and downs in his remarks and his behaviour.

"(But) the foundations of the JCPOA (nuclear deal) have been so strong that during these 15 months of pressure... the structure has remained solid."

The other partners to the agreement -- Britain, France, Germany, China, Russia and the EU -- all agree that Iran has stuck by its commitments, as does the International Atomic Energy Association which is tasked with inspecting Iran's compliance.