The last day of registration for Iran's presidential candidates began on Saturday with several high-profile figures yet to declare whether they would run in the most uncertain election in decades.

The 14 June poll will be the first presidential election in Iran since 2009, when mass protests dubbed the "Green Movement" erupted after the disputed re-election of Mahmoud Ahmadinejad over reformist candidates Mirhossein Mousavi and Mehdi Karoubi.

Since then, reformists who espouse greater social and political freedoms have been suppressed or sidelined. Mousavi, his wife and Karoubi have been under house arrest for more than two years.

Now, the prestige of Iran's most powerful man, Supreme Leader Ayatollah Ali Khamenei, is threatened by intense rivalry between hardline groups polarised by Ahmadinejad, who has been accused of wanting to erode the system of clerical rule.

Early on Saturday, Iranian media reported the registration of the charismatic mayor of Tehran, Mohammad Baqer Qalibaf, a member of a three-man coalition of "Principlists" - loyal defenders of Khamenei and the theocratic system who are, by implication, hostile to Ahmadinejad.

Another coalition member, Gholam-Ali Haddad-Adel, registered on Friday and the third, Ali Akbar Velayati - a former foreign minister and adviser to Khamenei - was expected to register on Saturday.

About 400 candidates have registered so far, including moderate cleric Hassan Rohani, a former nuclear negotiator under reformist president Mohammad Khatami, and several other reformists including former member of parliament Mostafa Kavakebian and Mohammad Aref, a vice president under Khatami.

Two other Principlists, Mohammad Hassan Abu-Torabi Fard and former health minister Kamran Baqeri Lankarani, are also running, as is Mohsen Rezaie, who headed the Revolutionary Guards and lost to Ahmadinejad in 2009.

But the biggest political hitters have left it to the last minute to make their decision.

RAFSANJANI RETURN?

Feverish speculation surrounds several potential candidates, including Khatami, who retains much popularity but is viewed with suspicion by conservatives for his support of Mousavi four years ago. Khatami has not officially ruled himself out but on Friday endorsed former centrist president Akbar Hashemi Rafsanjani and said he hoped he would run.

Rafsanjani, 78, has indicated he may run but only if the supreme leader consents. He has some support among reformists because of his support for the opposition movement in 2009.

"The chance of Mr Rafsanjani becoming a candidate is not small," said Mohammad Hossein Ziya, who campaigned in 2009 for Karoubi and now runs his website from the United States. "If Mr Rafsanjani becomes a candidate, I think the reformists and some portion of the Principlists will support him."

The leadership around Khamenei especially fears a campaign by Ahmadinejad aide Esfandiar Rahim Mashaie, viewed with intense distrust by conservatives who see him as leading a "deviant current" that seeks to set aside clerical influence in favour of secular nationalism.

All candidates must be vetted by a conservative body of clerics and jurists known as the Guardian Council, which can disqualify any candidate without offering a justification. It typically narrows the field to just a handful of men. Only eight women have registered so far.

But there appears to be little of the popular enthusiasm for the vote that there was in the run-up to the 2009 election, when many sensed a possibility of real change.

After years of ever tougher international sanctions over Tehran's nuclear programme, many Iranians care more about the economy than political infighting.

"A large portion of people either don't want to participate or they are so worried about economic issues that they don't see political activities as a priority," Ziya said.

But he added: "People are watching and waiting to see who runs, and for this reason we still cannot say what people think."