Afghanistan's presidential elections, due to take place in May, have been postponed until August 20 due to security and logistical problems.

The decision to delay the elections, announced on Thursday by the Independent Election Commission, was attributed to a clause in the constitution citing that a lack of security makes a vote impossible.

Other Afghan officials have said the delay is due to not having time to declare candidates, print ballots and distribute them around the country by May.

Hamid Karzai, Afghanistan's president since a US-led invasion removed the Taliban in 2001, has confirmed he will run for a second term.

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.