President Ahmadinejad has become the first Iranian leader to perform the haj.

Mr Ahmadinejad was asked by King Abdullah of Saudi Arabia, a close US ally, to join nearly two million Muslims at the annual pilgrimage to Mecca.

Islam requires all physically able Muslims to perform the journey at least once, if they can afford it, but Mr Ahmadinejad is the first President of Shia-dominated Iran to make this expedition to Sunni-governed Saudi Arabia.

The haj has traditionally been the focal point for the frosty relations between the two countries. In 1987, during an Iranian demonstration at the pilgrimage, security forces tried to break up the protest and more than 400 people, including 275 Iranians, were killed. The following year Tehran and Riyadh ended diplomatic relations and Iranian pilgrims stayed away from Mecca for four years.

More recently the two countries have given an impression of unity, vowing to work together to end the political crisis in Lebanon and bring stability to Iraq. The President’s visit could be seen as a consolidation of the warming relations.

Mr Ahmadinejad was due to join those gathering on Mount Arafat today to pray for Allah’s forgiveness and symbolically wait for the last judgment, but heavy traffic stopped his appearance.

“If I made a mistake or in one of my speeches said something that was not in line with the interest of the nation and has hurt the nation, or I was not able to defend its rights, then I ask people to forgive me," Mr Ahmadinejad said before leaving Iran.

His pilgrimage will encompass all the sacred rituals associated with the haj, including walking seven times anti-clockwise around the Kaaba, the square structure, at the Grand Mosque.

The annual pilgrimage has been plagued by safety concerns in the past few years. Last year 364 people were killed in a stampede at the entrance to the Jamarat Bridge, where pilgrims traditionally stone the pillars in the mosque to ward off the devil.

Saudi officials say that tightened security, improved safety measures and increased crowd control this year mean that the bridge can now handle up to 200,000 people crossing every hour. About 1,708,000 pilgrims from 181 different countries have travelled to Saudi Arabia for the haj this year, according to official reports, an increase of 3 per cent on 2006.