Supporters of Mir Hossein Mousavi, the defeated main opposition candidate in Iran's presidential election, have called for a protest outside parliament in Tehran in defiance of a government ban.
The rally was scheduled for 4pm (11:30 GMT) on Wednesday in one of the capital's main squares after the Guardian Council, Iran's highest legislative body, said that the results of the disputed poll would not be annulled.
The planned gathering will be a key test of whether a government crackdown, which has left at least 19 people dead, has quelled the angry demonstrations that followed the re-election of Mahmoud Ahmadinejad, the incumbent president.
Although streets protests have diminished since police and pro-government militias used tear gas, batons and water cannon against protesters on Saturday, calls for further protests among supporters of Ahmadinejad's opponents have continued.
Cries of "Allahu Akbar" (God is great) were again heard across Tehran overnight, a symbolic gesture echoing a tactic used during the Islamic revolution in 1979.
Nazenin Ansari, the diplomatic editor of the Kahylan newspaper, told Al Jazeera that the fall in numbers gathering to protest was understandable given the "degree of repression on the streets".
"Without a doubt, although there are not millions gathering on the streets because of the indiscrimante fire and repression, this is going to transform," she said.
"In provinces, where people were before gathering in universities, in recent days were are seeing people gathering in main squares."
Mousavi, a former prime minister, and the two other candidates in the election have all filed complaints to the Guardian Council about alleged problems with the June 12 vote.
But on Wednesday, Mohsen Rezaie, the conservative candidate who finished third in the election, withdrew his objections.
"I see it as my responsibility to encourage myself and others to control the current situation," the official IRNA news agency reported Rezaie as saying in a letter to the Guardian Council.
"Therefore I announce that I'm withdrawing my submitted complaints," the former head of the Revolutionary Guard said.
Rezai had originally complained that he had won more votes than he had been credited with when the interior ministry declared the results.
"I think he wants to remain in the framework of the Islamic republic - the framework that conservative newspapers are trying to push Mousavi and Karroubi out of," Al Jazeera's Alireza Ronaghi, reporting from Tehran, said.
"Mohsen Rezaie intends to stay close to the core of the Islamic republic and shwo his allegiance to the supreme leader by obeying his call that the elections are over."
'No major fraud'
Despite Ayatollah Ali Khamenei, Iran's supreme leader, agreeing to extend the deadline for filing election complaints by five days, a spokesman for the Guardian Council has said that there will not be a fresh vote.
"If a major breach occurs in an election, the Guardian Council may annul the votes that come out of a particular affected ballot box, polling station, district or city," Abbas Ali Kadkhodaei was quoted as saying by Press TV, an Iranian government-funded station.
"Fortunately, in the recent presidential election we found no witness of major fraud or breach in the election. Therefore, there is no possibility of an annulment taking place," he said.
Mehdi Karroubi, who came in fourth in the poll, according to official results, has called for Iranians to hold ceremonies on Thursday to mourn those killed in the protests.
His call came after Grand Ayatollah Hossein Ali Montazeri, a dissident religious leader who is under effective house arrest, announced three days of national mourning from Wednesday.
Montazeri was once named successor to Ayatollah Rohullah Khomeini, but fell out with the founder of the Islamic Republic shortly before his death in 1989.
Barack Obama, the US president, on Tuesday repeated his remarks that the world was watching events in Iran and said that how Tehran handles dissent from its own people "will help shape the tone, not only for Iran's future, but also its relationship to other countries".