Rival once one of Karzai's closest deputies

Abdullah Abdullah, the man who has forced Hamid Karzai into a second round of voting, was until three years ago one of his closest deputies.

The 41-year-old former ophthalmologist rose from being a key aide to a renowned Mujahideen commander to being Karzai's foreign minister.

After falling out with the President in 2006, he remained a central figure in Afghanistan's leading opposition group, which was based around the remnants of the civil war-era ethnic Tajik Northern Alliance.

After a hesitant start to his presidential campaign, he galvanised opposition to Karzai's deeply unpopular regime and secured 28 per cent of the vote in the August 20 election.

Softly spoken and urbane, he has since won respect from diplomats for urging his supporters away from violence despite clear evidence Karzai's officials had tried to steal the election.

Abdullah built his campaign on an agenda of thorough constitutional reform.

He has argued that by introducing a prime ministerial system and elected provincial governors he can decentralise power from Afghanistan's notoriously corrupt and ineffective government.

Abdullah studied medicine at Kabul University before joining the anti-Soviet resistance in the Panjshir Valley.

There he became a close adviser to the commander Ahmad Shah Massoud and served as foreign minister for the Northern Alliance. He continued the job under Karzai.

With a Pashtun father and Tajik mother, he hopes to straddle Afghanistan's ethnic divide, but many in the tribal south doubt his Pashtun credentials and are deeply suspicious of his ties to the Northern Alliance.