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Iranian opposition leader Mir Hossein Mousavi will create an umbrella group made up of reform-minded political parties, a top aide told The Associated Press on Tuesday in the most concrete indication yet of how he will move forward after a government crackdown crushed street protests.

Mousavi has said he will seek a "legal framework" for continuing his campaign against the government of President Mahmoud Ahmadinejad, which he and his supporters call illegitimate. But there's been no word on how he will do so.

His top aide Ali Reza Beheshti said Mousavi "has decided to set up a political front, made up of various reform-minded political groups."

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"The front will be actually a network to coordinate efforts by groups that seek to promote democracy and challenge hard-liners who impose their will on the nation in the name of Islam and democracy," he said.

Beheshti told AP that Mousavi was still working out details with other pro-reform leaders and plans to announce the new "political front" soon.

Ahmadinejad is due to be sworn into office for a second term sometime between Aug. 2 and 6, the vice speaker of parliament Mohammad Reza Bahonar said Tuesday, according to the state news agency IRNA. The inauguration would take place a day after a ceremony in which supreme leader Ayatollah Ali Khamenei officially approves him as president.

Mousavi claims to have won the election, saying official results showing a landslide victory for Ahmadinejad are fraudulent. Hundreds of thousands marched in days of street protests after the election denouncing the results, but they were largely shattered by a heavy government crackdown in which hundreds were arrested and 20 protesters were killed. Khamenei has declared the results valid.

Since then, Mousavi has stayed out of the public eye and has struggled for a way to harness the widespread discontent that remains over the vote. The reform movement is severely hampered in political action after many of its senior politicians were detained in the wave of arrests.

Mousavi met last week with the two other top leaders of the reform movement — Mahdi Karroubi, who also ran in the June 12 presidential election, and former president Mohammad Khatami. Karroubi's National Confidence Party and the Association of Combatant Clerics, to which Khatami belongs, would likely join the grouping along with other parties, particularly the Islamic Iran Participation Front.

The reformist daily Etemad-e-Melli, or National Confidence, said Mousavi and other prominent reformist leaders will attend a Friday prayer to be led by their main supporter, Akbar Hashemi Rafsanjani, a powerful cleric in the political establishment and former president.

Rafsanjani is scheduled to deliver the main Friday prayer sermon in Tehran this week for the first time since the election, giving him a prominent political platform — and both reformists and hard-liners are anxiously waiting to see what he will say and how he will end his silence over the turmoil. Whether he lends his support will be a key in shaping Mousavi's future political front.

Rafsanjani's younger brother, Mohammad Hashemi Rafsanjani, welcomed the formation of the umbrella group by Mousavi but warned that "there is ambiguity over how the ruling system will respond to this phenomenon."

Speaking to the AP on Tuesday, the younger Rafsanjani, a leader of the moderate Kargozaran-e-Sazandegi Party, said fraud in the election has divided the people and the ruling system.

"They imposed a police atmosphere. They treated the people in a distasteful and disrespectful way ... people were insulted. A long wall of mistrust has been shaped between the people and the ruling system," he said.