ROME -- The head of Iran's nuclear agency is warning the United States against undermining the 2015 nuclear deal, saying international nonproliferation efforts as well as Washington's global standing would suffer.

Iranian nuclear chief Ali Akbar Salehi told an international conference on enhancing nuclear safety Tuesday that Washington's recent "illusory negative postures do not augur well" for keeping the deal intact.

(From L to R) European Union High Representative for Foreign Affairs and Security Policy Federica Mogherini, Iranian Foreign Minister Mohammad Javad Zarif, Iran's nuclear chief Ali Akbar Salehi, Russian Foreign Minister Sergey Lavrov, British Foreign Secretary Philip Hammond and U.S. Secretary of State John Kerry pose for a picture at the United Nations in Vienna, Austria, July 14, 2015, after Iran and six major world powers reached a nuclear deal. Getty

He said Iran didn't want to see the deal unravel but that "much more is at stake for the entire international community than the national interests of Iran."

President Donald Trump is set to deliver a speech on Iran this week in which he is expected to decline to certify Iran's compliance in the landmark 2015 agreement, referring it to Congress, and perhaps targeting Iran's Revolutionary Guard with new sanctions.

The chief of the elite Guard warned on Monday that if the U.S. sanctions the force, America's military "should move its regional bases to a 2000-kilometer (1,240-mile) radius," out of the range of Iranian missiles.

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Jafari rejected the idea of negotiating with the U.S. over regional issues and said if the United States designates the Revolutionary Guard a terrorist group, the Guard -- which has suffered significant casualties fighting the Islamic State of Iraq and Syria (ISIS) -- will also consider the U.S. army a terrorist group.

He said such a move by the U.S. would eliminate "any chance for engagement forever."

On Saturday, Iran's president defended the nuclear deal and said not even 10 Donald Trumps can roll back its benefits to Iran.