Iran's presidential election, in which hardline Mahmoud Ahmadinejad was adjudged the winner over his moderate rival, Mirhossein Mousavi, has led to the broadest internal unrest since the 1979 Islamic revolution.
Iranian protesters have flooded the streets of Tehran and other cities over the past week. It remains unclear whether they will heed Supreme Leader Ayatollah Ali Khamenei, who demanded a halt to the rallies in an uncompromising speech on Friday.
Here are some questions and answers on what could happen next in the Islamic Republic, the world's fifth biggest oil exporter, whose nuclear program has alarmed the West.
* WILL THE AUTHORITIES CRACK DOWN HARDER?
This seems likely after Khamenei's steely Friday sermon in which he warned opposition politicians they would be responsible for any bloodshed if protests continued against the June 12 poll, which he said Ahmadinejad had won fairly by 11 million votes.
A senior police commander said on Saturday any further protests would be illegal and police would act firmly.
The authorities had allowed many of the huge marches of the past week to proceed, in the hope they would die down.
However, human rights groups say police and religious militia have sometimes attacked largely peaceful demonstrators. Hundreds of opposition and reformist activists have been detained.
Other signs of a crackdown have included attacks by security forces and militias on university dormitories, severe disruption of internet and mobile telephone communications, and curbs on international and domestic media, the rights groups say.
The authorities can call on the elite Revolutionary Guard, the religious basij militia, police and other forces considered loyal to Khamenei and Ahmadinejad to crush dissent.
WILL THE PROTESTS CONTINUE?
It is not clear yet that the hundreds of thousands of Iranians who have protested in Tehran and elsewhere are ready to cool their anger over an election that Mousavi says was rigged.
Mousavi and another losing candidate, liberal cleric Mehdi Karoubi, have called for the vote to be annulled.
The anti-Ahmadinejad camp has support from a broad coalition of moderates and conservatives within Iran's religious and political establishment, including former presidents Mohammad Khatami and Akbar Hashemi Rafsanjani, Parliament Speaker Ali Larijani and Mohammad Baqer Qalibaf, the mayor of Tehran.
Because Khamenei has thrown his weight behind Ahmadinejad, these establishment insiders will have to decide whether to pursue a course that could lead to much bloodshed.
They will also have to weigh the risks of an opposition campaign that would effectively challenge the authority of the Supreme Leader, a pillar of Iran's system of Islamic rule.
IS ANY COMPROMISE POSSIBLE?
It is hard to see any deal that could satisfy both sides, especially after Khamenei's harsh rhetoric on Friday.
But an offer by the Guardian Council, a watchdog body which must certify the election result, to recount a random 10 percent of the votes in the presence of representatives of the defeated candidates, might open the door for a face-saving solution.
The council, composed of 12 clerics, half of them appointed by Khamenei, had invited the three candidates to discuss their complaints on Saturday, but only Mohsen Rezaie, a conservative former Revolutionary Guard commander, showed up.
The council had said previously it was only willing to recount some disputed ballot boxes, not re-run the election, which official results showed Ahmadinejad had won with nearly 63 percent of the vote, against 34 percent for Mousavi.
COULD KHAMENEI BECOME A TARGET?
The Supreme Leader, who has usually preferred to rule from behind the scenes, has thrust himself into the thick of the political conflict by siding so openly with Ahmadinejad.
Khamenei has enormous powers, far outweighing those of the president, but one body, the 86-man Council of Experts, does have the authority -- never previously used -- to depose him.
Rafsanjani presides over this body of clerics, but it is not clear whether the wily politician would be able or willing to muster a majority for a constitutional challenge to Khamenei.