Mahmoud Ahmadinejad said he had evidence of collaboration

Mr Ahmadinejad said the "internal elements" would be exposed if they did not stop pressurising his government, in a speech at a university in Tehran.

Reformists and several senior clerics have challenged Iran's nuclear policy.

Last week, Mr Ahmadinejad was quoted as claiming his government's critics were less intelligent "than a little goat".

The comparison was made in a speech he made in South Khorasan province on Wednesday, according to Farda, an Iranian website affiliated to so-called pragmatic conservatives.

Although the remarks were reported by a number of conservative and pro-reform newspapers, Mr Ahmadinejad's spokesman has insisted he was misquoted in an example of "press charlatanism".

'Traitors'

In his speech at Tehran's Science and Technology University, Mr Ahmadinejad said he had no intention of halting Iran's nuclear programme despite warnings by rival politicians and several clerics of the serious threats facing the country.

The UN Security Council has imposed sanctions on Iran because of fears it is seeking to develop nuclear weapons, while the US has not ruled out military action.

We even have a recorded speech of one of them who tells the enemy: 'Why should you give up?... Step up pressure to make [Iran] retreat'

Iranian President Mahmoud Ahmadinejad

New push over Iran row

"These people are traitors and, based on our pact with the nation, we will not back down," he said, according to the official news agency, Irna.

"If they do not give up their pressures on [the government] over the atomic issues, we will expose them to the Iranian nation," he added.

"These are traitors and, in accordance with the vows we have taken to the nation, we will not back down and be onlookers."

Mr Ahmadinejad said he had chosen not to reveal their identities "because of some sensitivities", but warned he would do so "upon closure of the nuclear issue".

"They sent people to the enemy to regularly give them information from within the ruling system every week. We even have a recorded speech of one of them who tells the enemy: 'Why should you give up?... Step up pressure to make [Iran] retreat'," he claimed.

'Dangerous'

The president also said his critics had pressurised a judge "to acquit a suspect for spying", which correspondents say might be a reference to Hossein Mousavian, the former top nuclear negotiator who was detained in May for "security reasons".

Mr Rafsanjani has warned of the serious threats facing Iran

Mr Mousavian is an ally of former President Akbar Hashemi Rafsanjani, who recently voiced concerns about a military attack.

"The danger is serious and everyone should try to preserve the country's interests," Mr Rafsanjani said two weeks ago.

On Thursday, Mr Ahmadinejad's predecessor, Mohammad Khatami, warned of an escalating crisis between Iran and the international community.

"Ruling the country by those who impose their ideas is very dangerous," he told a gathering of reformist leaders.

Iran's former top nuclear negotiator, Ali Larijani, resigned last month over reported disagreements with Mr Ahmadinejad on how to proceed on the nuclear issue.