Iran's president said Wednesday that the world needs its help to stabilise a troubled Middle East, in remarks pointing to the wider ramifications of a deal over Tehran's disputed nuclear programme.

In a live televised speech marking the anniversary of the 1979 Islamic revolution, Hassan Rouhani implicitly linked ongoing nuclear talks with world powers to resolving bloody conflicts in Iraq and Syria.

Significant gaps remain between Iran and the United States and other leading nations on specific measures to end a 12-year standoff on the nuclear issue, but both sides are pushing for a deal.

And although Iranian and US officials have said the turmoil gripping the Middle East falls outside the remit of negotiations, analysts say both governments acknowledge an agreement could have a broader impact.

"If there is going to be peace and stability in the region, and terrorism is to be uprooted, there is no other way than with the presence of the Islamic Republic of Iran," Rouhani said.

A huge crowd filled Azadi (Freedom) Square in Tehran to hear the Iranian president commemorate the tumultuous events that ousted Shah Mohammad Reza Pahlavi from power 36 years ago.

The fall of the shah was followed months later by the storming of the US embassy in Tehran by Islamist students, culminating in American diplomats being held prisoner.

The crisis, which lasted 444 days, caused US-Iranian diplomatic relations to be severed and it ushered in deep distrust which persists to this day.

This year's anniversary was the second to coincide with an intense diplomatic effort to end the nuclear deadlock but the first since jihadists of the Islamic State group seized large parts of Iraq and Syrian territory.

- Nuclear agreement 'win-win' -

When IS overran northern Iraq in June, predominantly Shiite Iran provided weapons and assistance to Kurdish fighters and sent military advisers to Baghdad.

Iran has also backed Syrian President Bashar al-Assad in his battle against rebels, including jihadists.

Referring to the fight against IS as well as longstanding instability in Yemen and Lebanon, Rouhani said Iran was playing a leading regional role.

"You've seen in Iraq, Syria, Lebanon and Yemen that the power that could help those nations against terrorist groups was the Islamic Republic of Iran," he said.

Rouhani then raised the issue of the nuclear talks and the lifting of sanctions imposed on Iran for pursuing its atomic programme.

"What we are offering is to reach a win-win agreement in which Iran will show transparency in its peaceful nuclear activities," he said.

"And the other side must end its wrong, inhumane and illegal sanctions. This is in the interest of both sides. They too need this."

An interim agreement in November 2013 saw Iran agree to curb some nuclear activities in exchange for limited relief from Western sanctions, but two deadlines for a comprehensive deal have been missed.

- US, British, Israeli flags burned -

The political outline of an agreement is now due by March 31 and the final accord by June 30.

Western governments have long suspected Iran of covertly pursuing a nuclear weapons capability, allegations denied by Tehran, which insists its activities are for energy production only.

The interim deal and subsequent talks stand in stark contrast to eight years of stalled negotiations and escalating sanctions under Rouhani's hardline predecessor Mahmoud Ahmadinejad.

Rouhani has the support of supreme leader Ayatollah Ali Khamenei, but hardliners in Tehran regularly argue Iran has already conceded too much by accepting limits on its nuclear programme.

Rouhani and his Foreign Minister Mohammad Javad Zarif have also come under fire at home for their overtures to the United States, long derided as the "Great Satan".

On Wednesday, as is customary at major rallies, US, British and Israeli flags were burned.

And in a nod to the Islamic republic's origins, Rouhani said nothing could diminish its characteristics.

"The roots and principles of the revolution remain unchangeable," he said.

Zarif, also at Azadi Square, said what was needed for a historic nuclear agreement was political will from the major powers.

"If they have the will, we can reach an agreement today. If not, the negotiations will not succeed, even in 10 years," he said.

US ex-lawmaker says made pioneering visit to Iran
Washington (AFP) Feb 9, 2015 - A former US congressman visited Iran in December, the first time a current or former American lawmaker was invited to the Islamic republic since its 1979 revolution, he said Monday.

"The Iranians are deeply concerned about respect, the one thing they yearn for is respect," Jim Slattery, 66, said at a presentation at the Atlantic Council think-tank.

His Iranian hosts, he said, assured Slattery he was the first US lawmaker invited to the country since the Islamic Revolution ousted the Washington-backed shah.

The Kansas Democrat, who served in the House of Representatives from 1983 to 1995, attended an international conference in Tehran against violence and extremism.

He also met with Iranian officials, including key members of Parliament.

President Hassan Rohani and his inner circle are "deeply committed to improving this relationship with the United States," he said.

"And I believe that if they fail, we are likely to see the return of a much more hard-line government in Iran."

The visit was particularly timely in that it occurred in the midst of intense international negotiations on resolving a long-running dispute over Iran's nuclear operations.

The Iranian officials he met were "all deeply concerned about what effect Congress elections last November will have on President (Barack) Obama's capacity to actually implement any agreement" on reining in Iran's nuclear program.

"They are very troubled by the prospect of... putting their best deal on the table," only to have US lawmakers reject it.

"This would be a political disaster," Slattery added. "So they need assurances that if there is a deal that is worked out, they want to be confident that it can actually be approved and implemented by the Obama administration."

November's elections gave Republicans full control of Congress, and several lawmakers seek to challenge Obama by passing legislation imposing new sanctions against Iran before conclusion of the nuclear negotiations.

Slattery argued that both Tehran and Washington bore responsibility for obstacles to an international deal.

"Very few members of our administration... have any personal relationships with Iranians," he stressed.

"One of the great problems we have to overcome right now is ignorance."

Slattery suggested a path for dialogue through religion, a dominant force in the two countries.

"Religion is a big part of their life, just as it is in Kansas," he said.

"Isn't there a space here for conversation?"