US Secretary of State John Kerry has arrived in Kabul to discuss Afghanistan's disputed presidential run-off election.

Kerry will meet candidates Abdullah Abdullah and Ashraf Ghani - and, with outgoing President Hamid Karzai. Citing preliminary results, Ghani was declared the winner. Abdullah has alleged massive voter fraud - amid reports that he plans to build a "parallel government".

Washington has suggested that failure to resolve the dispute jeopardizes billions in US aid to Afghanistan.