Conservative Mahmoud Ahmadinejad became Iran's new president today, taking office amid international turmoil over Tehran's nuclear ambitions and his own past.
The 48-year-old conservative former mayor of Tehran, deeply loyal to the values of Iran's 1979 Islamic revolution, won a landslide election victory in June and was appointed president by Supreme Leader Ayatollah Ali Khamenei.
Iran's President Mahmoud Ahmadinejad
Mr Ahmadinejad was warmly embraced by the leader before reaffirming his pledge to fight for the common man. "As a servant of the republic and a drop in the endless ocean of the Iranian nation ... I commit myself to respond to the trust and hopes of such a nation by serving them honestly," he told Iran's leading figures assembled at his investiture.
The president in Iran appoints ministers who manage the day-to-day business of government. But the government's power is checked by a number of unelected bodies answerable to Ayatollah Khamenei, the most powerful figure in Iran who is appointed for life.
Mr Ahmadinejad, a former member of the Revolutionary Guard, takes an oath of office at a further ceremony on Saturday at which he is due to announce his cabinet.
He takes over the government as Iran edges closer to possible UN Security Council sanctions over its nuclear programme, which Washington says is a smokescreen for building atomic bombs. Tehran insists its ambitions are peaceful.
In order to break this impasse, EU diplomats have been trying to get Iran to surrender its nuclear fuel work in return for economic incentives. But Iran says such a compromise is unacceptable and a spokesman said it hopes to resume nuclear fuel work today, a move that threatens to end EU mediation.
In Iran's opaque political system, analysts are split on whether top policy makers are somehow setting the stage for Mr Ahmadinejad to save the day with a new deal or whether he is subservient to their greater national goals.
If this mounting international pressure on the nuclear programme was not enough, Mr Ahmadinejad also faces numerous accusations about his past. The United States thinks he played a key role in the storming of its embassy in Tehran after the revolution, something which he and those who took part deny.
Austrian investigators are looking into whether he was involved in the murder of Kurdish dissidents in Vienna in 1989. Again, his aides deny the charges.
Mr Ahmadinejad also faces massive economic challenges in a country where growth is slipping and oilfields, the country's lifeblood, are losing capacity.