Factbox: Choices curtailed - Iran's parliamentary election

Iranians voted on Friday in a parliamentary election likely to reinforce the authority of Supreme Leader Ayatollah Ali Khamenei, amid mounting U.S. pressure over the nuclear program and as discontent grows at home.

Pro-reform and leading conservative hopefuls were barred, leaving voters a choice only between hardline and low-key conservatives loyal to Khamenei. Both back the ruling theocracy, but conservatives support engagement with the outside world.

Moderates and pragmatists seeking greater political and social freedoms have mostly been barred.

Here are some facts about Iran's 11th parliamentary election since the 1979 Islamic revolution:

CANDIDATES VETTED

About 7,150 candidates from more than 16,000 hopefuls survived screening by government-run panels and the Guardian Council, a conservative body of clerics and jurists who assess commitment to Islam, belief in the system of religious law and the Islamic Republic.

A third of incumbents were barred from standing again. Moderates, who see disqualifications as a bid by hardliners to dominate the 2021 presidential race, had no candidates in the contest for 230 of the assembly's 290 seats.

POLITICAL PARTIES, COALITIONS AND FACTIONS

Despite 82 national political parties and 34 provincial parties counted by the interior ministry, Iran lacks a tradition of disciplined party membership or detailed party platforms, and politics runs along factional lines. 

Months of haggling left two main hardline groups and one conservative coalition, with some candidates backed by more than one group.

COALITION OF ISLAMIC REVOLUTION FORCES

The biggest hardline group, comprising former members of the elite Revolutionary Guards and their affiliated Basij militia, as well as other Khamenei loyalists, is expected to dominate the assembly.

PRINCIPALISTS

These are conservatives, who label themselves "principle-oriented" politicians for their loyalty to the ideals of the Islamic Republic and Khamenei but differ from hardliners in being less hostile to the West.

FRONT OF ISLAMIC REVOLUTION STABILITY

Seen as the extreme end of the Islamic fundamentalist camp, the group is affiliated to one of the most radical figures in the religious establishment, Ayatollah Mohammad Taqi Mesbah-Yazdi.

EXECUTIVES OF THE CONSTRUCTION OF IRAN

Technocrats who support the Islamic Republic's ideals but who also want social and political change. The vetting process doomed their hope for a significant voice in parliament, as it winnowed out their leading candidates. Along with some low-key moderate parties, they have a list of 30 candidates for Tehran.