Iranian President Mahmoud Ahmadinejad said on Sunday Tehran would not negotiate about its disputed nuclear programme under pressure, but would talk to its adversaries if they stopped "pointing the gun".

In a speech to mark the 34th anniversary of the Islamic revolution, Ahmadinejad struck a more conciliatory tone than Supreme Leader Ayatollah Ali Khamenei, who on February 7 rebuffed a US call for direct negotiations on disputes between the two countries.

Ahmadinejad does not have the authority to authorise negotiations over the nuclear programme, which lies with Khamenei.

"You cannot point a gun at the Iranian nation and then expect them to have negotiations with you," Ahmadinejad said, speaking to a crowd gathered in Tehran's Azadi (Freedom) Square.

His speech, which partly dealt with Iran's policy towards its 'enemies', was carried live on Iranian state television.

"Talks should not be used as a lever to impose one's opinions.... If you stop pointing the gun at the Iranian nation, I will negotiate (with you) myself," he added.

The US and some of its allies suspect Iran may be trying to develop atomic weapons capability under the cover of a civilian nuclear energy programme, a charge Iran has denied.

Many believe no nuclear deal is possible without a US-Iranian thaw, requiring direct talks addressing myriad sources of mutual mistrust and hostility lingering since Iran's 1979 Islamic Revolution and the hostage crisis at the US embassy in Tehran.

On the nuclear dispute, Iran has agreed to a new round of talks with world powers in Kazakhstan on February 26.

ENEMIES "WILL NOT SUCCEED"

Tehran is seeking the lifting of sanctions that have slashed oil exports and helped reduce the value of the Iranian rial by about half in the last year, contributing to higher inflation and weakened purchasing power for ordinary Iranians.

Iranians bearing banners saying "Down With USA" and "We are standing until the end" gathered at state-organised mass demonstrations in the capital Tehran and other major cities to mark the anniversary of the ousting of a Western-friendly monarchy in favour of clerical leadership.

Ahmadinejad did not address the specifics of Iran's nuclear programme, or of the planned talks, in his speech on Sunday. He said that Iran would counter the sanctions by increasing its non-oil exports and weaning itself off crude revenues.

"Today the enemies are trying their utmost to put pressure on the Iranian nation to stop its progress but they will not succeed," he said.

Last week, the US implemented a measure meant to "lock up" Iranian oil revenues by requiring them to be credited to accounts in countries that buy Iranian crude.

Supreme leader Khamenei on Thursday slapped down an offer of direct negotiations with the United States, saying negotiations and pressure were incompatible.

Khamenei was believed to have been replying to remarks by Vice President Joe Biden, who said in a speech in Germany on February 2 that the United States was ready to hold direct talks with Iran if it was serious about negotiations. – Reuters