Iran's Rouhani says Trump pledge to renegotiate nuclear deal 'meaningless'

Iranian President Hassan Rouhani said on Tuesday US President-elect Trump cannot unilaterally cancel the nuclear deal Tehran signed with world powers including Washington and that talk of renegotiating it was "meaningless".

Trump, who will take office on Friday, has called the July 2015 agreement "the worst deal ever negotiated". He has threatened to either scrap the agreement or seek a better deal.

Under Iran's agreement with the United States, France, Germany, Britain, Russia and China, Tehran agreed to shrink its nuclear programme to satisfy the powers that it could not be put to developing atomic bombs. In exchange, Iran received relief from sanctions, most of which were lifted in January 2016.

"The president elect has shown he is not happy about the nuclear deal, calling it the worst deal ever signed. This is only empty talk," Rouhani told a news conference on the anniversary of the removal of sanctions.

"I don't think he can do much when he goes to the White House," added Rouhani, who, through the diplomatic opening engineered a thaw in the Islamic Republic's long antagonistic relations with the West.

Rouhani said he was hopeful about the future of the nuclear deal, which has been buttressed by a UN Security Council resolution, calling talk about renegotiation "meaningless."

"I am optimistic about the future of the nuclear deal ... (It) is good for the United States, but he (Trump) doesn't understand," said Rouhani, whose remarks were broadcast live on state television.

Rex Tillerson, Trump's nominee for US Secretary of State, said last week that he would recommend a "full review" of the nuclear deal but did not call for an outright rejection.

Outgoing US President Barack Obama on Monday marked the first anniversary of the nuclear deal with Iran by emphasising its "significant and concrete results" and warning against undoing a pact supported by the world's major powers.

In language that seemed directed at Trump, who is set to take office on Friday, Obama said "the United States must remember that this agreement was the result of years of work, and represents an agreement between the world's major powers - not simply the United States and Iran."

He said the deal had "achieved significant, concrete results in making the United States and the world a safer place" and "verifiably prevents Iran from obtaining a nuclear weapon."

Such a diplomatic solution, he added, was "far preferable to an unconstrained Iranian nuclear programme or another war in the Middle East".

Helga Schmid, Secretary General of the European Union's foreign policy service in Brussels, said on Tuesday Trump's foreign policy team had misunderstood the nuclear deal and that it was not up for renegotiation.

"It's a multilateral agreement that cannot be renegotiated bilaterally," she said, pointing out that the deal had also been endorsed by the U.N. Security Council.

Despite their often fraught ties, the EU says it is in full agreement with China and Russia over the need to preserve the deal, which could also open up the Iranian market after a decade of sanctions, a prospect both Tehran and foreign firms welcome.