The founder of the Islamic republic, Ayatollah Ruhollah Khomeini, designated the last Friday of Ramadan as a day for Iranians and Muslims to demonstrate solidarity with the Palestinian people and their cause.
But this year, Quds Day (Jerusalem Day) could instead reexpose the fissures that exist as a result of Iran's severe political crisis.
Amid official warnings not to turn Quds Day into a protest against President Mahmud Ahmadinejad, whose reelection led to massive street protests that were met with a violent crackdown, three leading opposition figures say they will join the pro-Palestinian mass rally on September 18.
The leaders of the opposition movement, former presidential candidates Mir Hossein Musavi and Mehdi Karrubi, and former President Mohammad Khatami -- who have said Ahmadinejad's reelection was the result of massive fraud -- have announced that they will take part in the demonstrations in Tehran.
We want to tell Khamenei and other leaders that we're not supporting them, so don't show off to the world
The announcements have encouraged the members of the opposition Green movement while adding to the concern of the authorities. The opening of universities next week could potentially lead to more protests by the Green movement, and Tehran is also anticipating a strong protest against Ahmadinejad when he travels to New York next week to attend the general debate of the 64th session of the UN General Assembly. Friday Prayers
But for now the focus is on Quds Day, for which the authorities have already taken measures to avoid renewed protests by Musavi's and Karrubi's supporters.
Former President Ali Akbar Hashemi Rafsanjani has reportedly been banned by the authorities from leading the Friday Prayers during Quds Day. Rafsanjani, who has expressed support for the opposition movement, is a traditional speaker on Quds Day. He's been replaced by a hard-line cleric, Ahmad Khatami, and Ahmadinejad, who will be the key speaker before the prayers.
A statement posted on the website of the opposition "Mowjcamp" has described Ahmadinejad's speech as "a gift to the Greens." The statement suggests that members of the opposition can use the speech to chant "Allah Akbar" and "death to the dictator" and demonstrate that they didn't vote for Ahmadinejad.
Authorities, including Iran's police chief Esmail Ahmadi Moghadam, have warned to the opposition against "derailing" Quds Day.
On September 11, Iran's supreme leader, Ayatollah Khamenei, warned against creating divisions on Quds Day.
Khamenei said that Quds Day is a symbol of the Iranian nation's unity. “Be careful [to make sure] that some will not use the Quds Day celebration to create discord," he added.
Nevertheless, members of the opposition have vowed to turn Quds Day "Green," the color which has come to represent all those opposing the Iranian president. A slogan of one poster seen on the streets ahead of the event says: "No to Gaza, No to Lebanon. May my life be sacrificed for Iran."Poster Campaign
Mohammad in Tehran, a supporter of Musavi's "Green path of hope," tells RFE/RL he plans to join the Friday demonstration not to support the Palestinians but to call for freedom. "We want to tell Khamenei and other leaders that we're not supporting them, so don't show off to the world," he said.
Reformist journalist Mohammad Sadegh Javadi Hesar tells Radio Farda that the opposition can use Quds Day to demonstrate its readiness to resist state pressure.
"If people come to the scene on this day with intelligence and united, they can once more demonstrate the potential that we saw in Tehran, and in other cities too," he said in a telephone interview from Mashad.
A poster from an opposition Internet campaign: "Neither Gaza, Nor Lebanon -- My Life Is Devoted to Iran"
In recent days, leaflets have been distributed in several cities, posters have been plastered on walls, and there's been an online campaign to call on Iranians to take to the streets in protest.
A video making the rounds
shows a young woman in a bus reading from an opposition Quds Day flyer: "I call on all fathers, mothers, and whoever feels responsible [to protest] on Friday, September 18. I hope to see all of you on Friday," she says.
An mass opposition turnout would raise the risk of clashes with pro-government forces. There are already concerns that the government could use its plainclothes security agents to break up protests by the opposition.
The last time the opposition came out en masse was on July 17, when Rafsanjani led the Friday Prayers. Tens of thousands of citizens took to the streets in the capital and chanted slogans against Ahmadinejad and Ayatollah Khamenei.
Observers believe a large anti-Ahmadinejad protest on Quds Day would be another embarrassment for the hard-line faction of the Iranian establishment, which has tried to legitimize the president by putting reformists and intellectuals on trial for their alleged roles in the postelection unrest, accusing them of fomenting a "velvet coup."
A protest by the members of the Green movement would also publicly demonstrate the growing rift between the Iranian establishment and a large segment of the population. Ahmadinejad has said his government is Iran's most legitimate government in the past two decades.
That message will be hard to sell to many Iranians and rights activists who are planning to stage protests against the Iranian president on September 23 and 24 during his visit to New York.