Afghan President Hamid Karzai has called on the Taliban and their allies to vote in August elections rather than attempt to disrupt the nation's second presidential poll.

The 20 August vote is seen as a crucial moment for Mr Karzai's government and for Washington.

The US is sending thousands of extra troops this year as part of President Barack Obama's new regional strategy to defeat al-Qaeda and stabilise Afghanistan.

'I appeal to them (the Taliban) again and again to avoid any conflicts, not only during polling days but forever,' Mr Karzai said.

'Through elections we can bring peace and security, and through elections we can bring development,' he said.

The Taliban have repeatedly rejected the election as a Western-inspired sham.

They have also rejected Mr Karzai's calls for them to join the peace process, saying no talks can take place until all foreign troops have left the country.

The US has already almost doubled the number of its troops from the 32,000 in the country in late 2008 in order to secure the elections and to combat a growing Taliban insurgency.