The vote will be Afghanistan's second ever democratic election to choose a head of state.

Waning popularity

Other Afghan politicians are expected to take part in the presidential race, but none are expected to present much of a challenge to Karzai, despite increasing criticism of his governance from both inside Afghanistan and amid western allies.

Azizullah Loden, the head of the Independent Election Commission, said additional international forces would arrive in the coming months to boost security, allowing the vote to take place.

US military leaders have said that up to 30,000 new US forces could be sent to Afghanistan this year in an attempt to improve national security.

Thousands of those troops will be sent to the south, Afghanistan's most violent region.

Karzai was chosen to head up the Afghan transitional government and won 55 per cent of the vote in the country's first presidential elections back in 2004.

But his rule has been weakened by a failure to tackle corruption and violence, such as the resurgence of Taliban fighters who clash daily with Afghan government and international Nato troops.

While an election delay had been expected, opposition groups may raise objections.