By Parisa Hafezi
TEHRAN, June 25 Iran's leaders may have weathered the biggest anti-government protests since the 1979 Islamic revolution for now, but the unrest has revealed deep splits within the ruling elite, challenging the legitimacy of the 30-year-old system.
Here are some questions and answers on what could happen next in the Islamic Republic, the world's fifth biggest oil exporter, whose nuclear programme has alarmed the West and Israel.
WHAT OPTIONS ARE LEFT FOR THE OPPOSITION?
A show of force by riot police and religious basij militia since Saturday has kept all but the most determined protesters off Tehran streets, but opposition leaders remain defiant.
Mousavi said on Thursday the nation had a "constitutional right" to protest against an election he said was rigged. A message on his website also complained the authorities had shut his newspaper, restricted access to his supporters and put him under pressure to revoke his call for the vote to be annulled. The Guardian Council, which must rule on the result of the poll, has rejected that demand. Its final word is due on Monday.
It is hard to see scope for more legal challenges, short of attacking the position of the Supreme Leader himself.
Former President Akbar Hashemi Rafsanjani, a Mousavi ally, chairs the Assembly of Experts, which has the constitutional power to depose Khamenei. It has never tried to do so. Symbolic protests may continue.
People have taken to their rooftops nightly to call "Allahu Akbar (God is greatest)" and other slogans in a conscious echo of tactics used during the 1979 revolution.
Mousavi supporters plan to release thousands of balloons on Friday imprinted with the message "Neda, you will always remain in our hearts" -- a reference to a young woman killed last week who has become an icon of the anti-government movement.
There has been talk of other forms of civil disobedience, including strike action, but these have yet to materialise.
HOW CAN THE LEADERSHIP SHORE UP ITS POSITION?
So far the authorities have dealt with the protests using only some of the formidable armed forces at their disposal and could crack down harder if they felt this necessary.
Ahmadinejad has planted loyalists throughout a security and political apparatus increasingly dominated by the Revolutionary Guard, under Khamenei's ultimate control, analysts say.
If Mousavi and another losing candidate, Mehdi Karoubi, continue to defy Khamenei's orders to halt all protests, they could be arrested, along with other opposition figures.
But harsher methods would also further damage the legitimacy of the Islamic Republic's hybrid system of clerical rule and limited representative government, and might disquiet senior religious leaders who have stayed mostly silent so far.
Nevertheless, Mousavi is a veteran establishment insider and might back off if the system itself looked threatened.
Khamenei has given no ground so far, throwing all his weight behind Ahmadinejad, but once he feels more secure he might offer some concessions to placate and divide the opposition.
These might include releasing political prisoners, arresting those behind a bloody attack on a university dormitory or replacing some ultra-hardline members of the Guardian Council.
WHAT ABOUT OBAMA'S HOPES FOR DIALOGUE WITH IRAN?
The turmoil has dimmed immediate prospects for U.S. dialogue with Tehran, but have not snuffed out Obama's hopes for eventual engagement on the nuclear and other issues, U.S. officials say.
Ahmadinejad told Obama on Thursday not to meddle in Iran's internal affairs after the U.S. president said he was "appalled and outraged" by the past days of violence in the Islamic state.
"Do you want to speak (with Iran) with this tone? If that is your stance, then what is left to talk about?" he asked.
Iran has increasingly accused foreign powers, especially the United States and Britain, of fomenting the unrest at home.
But Western governments are in a quandary. They might not like Ahmadinejad, but still share important interests with Iran in promoting stability in neighbouring Afghanistan and Iraq.
And while the world watches the ferment in Iran, the centrifuges enriching uranium are still spinning -- to fuel nuclear power stations, as Iran says, or to acquire the knowhow to make atomic bombs, as the West suspects. (Writing by Alistair Lyon)