The United States remains Iran's "number one enemy" despite a recent nuclear deal with world powers, the chief of Tehran's top clerical committee said on Tuesday, Iranian media reported.

The Assembly of Experts is among Iran's most influential institutions, comprising 86 elected clerics who appoint and can dismiss the country's supreme leader.

It is led by the ultraconservative Ayatollah Mohammad Yazdi.

The nuclear agreement should not "change our foreign policy" of opposition to America, "our number one enemy, whose crimes are uncountable", Yazdi said in a speech opening the annual two-day assembly meeting.

"The US and Israel are the source of the situation in the region and (their) goal is to protect the Zionist regime in the Middle East," he was quoted as saying, blaming the two countries for the conflicts in Syria, Iraq and Yemen.

Echoing Yazdi's remarks, the leader of the Islamic republic's top military force, the Revolutionary Guards, said the US would always be "the Great Satan".

"Do not be fooled by the new American language," General Mohammad Ali Jafari told reporters.

"The hostility of the United States towards the Iranian people has not diminished, but actually increased... they use other methods," he added, according to the Guards website Sepah News.

President Hassan Rouhani, who as a cleric is also a member of the Assembly of Experts, took office in 2013 and has since reached out to the West for better relations.

The nuclear agreement reached on July 14 with six world powers -- Britain, China, France, Russia, the United States and Germany -- has helped revive Iran's political standing with the European countries.

Several high-level European delegations have visited Tehran since the deal.

But despite the nuclear talks and the intricate role US Secretary of State John Kerry played in getting the deal across the line, there is currently little prospect of normal relations.

The two countries severed ties in 1980 after the hostage taking of American diplomats by Islamist students.

Iran hopes nuclear deal propaganda will not sway US Congress
Tunis (AFP) Sept 1, 2015 - Iranian Foreign Minister Mohammad Javad Zarif said Tuesday he hoped the US Congress would not be swayed by "warmongers' propaganda" over the nuclear deal struck between Tehran and world powers.

"What happens in the US Congress, that's certainly a US issue," he told a news conference in Tunisia.

"We believe it's a mutually beneficial agreement," Zarif said of the July 14 accord on scaling down Iran's controversial nuclear programme in exchange for a lifting of international sanctions.

"And if people are not too much concerned with the propaganda being raged by warmongers in our region and outside our region, there's no reason for the deal to face any impediments in the United States," said the minister who negotiated the deal.

Congress is due to vote this month on whether to endorse the agreement between Iran and six world powers -- Britain, China, France, Germany, Russia and the United States.

Republicans strongly oppose the deal, saying it makes too many concessions to the Islamic republic and does so at the expense of the security of America and its chief ally Israel.

If the Republican-dominated Congress passes a resolution against the deal, President Barack Obama is expected to veto that move.

On the battle against the jihadist Islamic State (IS) group, in which arch-foes Tehran and Washington find themselves on the same side, Zarif called for a "multi-faceted" campaign.

"We believe and I think we agree with our Tunisian friends that the fight against ISIL is not simply a military operation," he said, using another name for IS.

"It has to be a multi-faceted cultural, religious, political, economic and if necessary military campaign against this threat," he said.

"We need to uproot the sources and the main reasons that give rise to this phenomenon."

IS has claimed responsibility for two major attacks in Tunisia this year in which 59 foreign tourists and a policeman were killed.