Tehran:
Iran's June 14 presidential election steps up a gear on Tuesday when the Guardians Council releases the approved list of candidates who have passed muster under the vetting process.
The unelected council, controlled by religious conservatives appointed by supreme leader Ayatollah Ali Khamenei, must ensure that all candidates meet certain conditions before being allowed to stand.
These conditions include being faithful to the principles of the Islamic republic and its official religion.
Most of the 686 men and women who registered to stand are expected to be disqualified.
Under Iranian presidential election law the Guardians Council will submit the names of those approved to the interior ministry, which organises the poll.
The ministry then has until Thursday to announce the names and campaigning begins the next day.
This year's poll comes four years after Mahmoud Ahmadinejad's disputed re-election for a second term sparked months of violent street protests.
Among the well-known figures who have registered are the moderate former president Akbar Hashemi Rafsanjani, and Esfandiar Rahim Mashaie, a close Ahmadinejad ally.
Both have been targeted by ultra-conservatives calling for their disqualification.
Ahmadinejad himself is constitutionally barred from seeking a third consecutive term.
Rafsanjani, who will be 79 in August, polarised Iran's complex political spectrum when he said he was considering standing again.
He has been isolated by ultra-conservatives since the massive street protests in 2009 sparked a heavy-handed regime crackdown and the arrest of hundreds of journalists, activists and reformist supporters.
At the time Rafsanjani called for those rounded up during the demonstrations to be released.
"If someone who wants to deal with the country's macro issues can only work a few hours per day, then it is natural that he will not be qualified," Guardians Council spokesman Abbas Ali Kadkhodaei was reported as saying in the media on Monday.
Rafsanjani's two consecutive presidential terms (1989-1997) were marked by reconstruction after the eight-year Iran-Iraq war and a relative openness to the West.
According to a Western diplomatic source, Rafsanjani is the main "proxy" candidate for the reformists.
He played an important role in the election of the reformist Mohammad Khatami, who succeeded him as president (1997-2005).
Khatami has repeatedly said he favours Rafsanjani's candidacy which should garner the support of moderate leaders and reformists.
A Western diplomat told AFP that Rafsanjani could also carve away votes from Mashaie as people prefer "their votes to be useful and not be considered just a vote," given Mashaie's slimmer chance of winning.
Mashaei has been targeted by hardliners for emphasising Persian civilisation rather than focusing on Islamic values.
In 2009, Khamenei overturned Mashaei's appointment as first vice president, sparking a rift between Ahmadinejad and conservatives loyal to Khamenei.
Mashaie cannot boast any economic success, since Ahmadinejad's second term has been marred by international sanctions over Tehran's controversial nuclear programme.
However, another Western diplomat said Mashaie can rely on Ahmadinejad's popularity among lower-income Iranians and on the support of a generation of civil servants who owe him their jobs.
Among potential conservative candidates, three names stand out: former foreign minister Ali Akbar Velayati, Tehran Mayor Mohammad Baqer Qalibaf and chief nuclear negotiator Saeed Jalili.
Velayati, 67, was foreign minister for 16 years from 1981 but appears to lack popular support, unlike the 51-year-old Qalibaf, who succeeded Ahmadinejad as mayor in 2005.
Iran-Iraq war veteran Qalibaf commanded the elite Revolutionary Guards air force and later became national police chief.
He has overseen huge projects in the capital, despite being denied government financing. However, some of Qalibaf's projects are deemed too Western for ultra-conservatives.
Jalili is close to the all-powerful Khamenei. His unexpected candidacy is supported by ultra-conservatives for his firmness in discussions with the great powers over Tehran's controversial atomic activities.
The West fears Iran's uranium enrichment is aimed at developing a military capacity, but Tehran denies this.
Jalili, 47, is also a veteran of the 1980s war with Iraq in which he lost his lower right leg. But political circles say he lacks both administrative experience and public support.