DHAKA: The US special envoy for Afghanistan is stepping down, Secretary of State John Kerry announced Wednesday in a move which comes at a key juncture in troubled US-Afghan ties.

James Dobbins, a veteran diplomat with deep ties to Afghanistan, is retiring after just over a year in office and will be replaced by his deputy Dan Feldman, Mr Kerry said in a statement, reports The Straits Times.

The shuffle comes as the two candidates to be Afghanistan's next president - succeeding Hamid Karzai who has held the reins for 13 years - wrangle over alleged fraud in the elections.

The political crisis threatens the country's first democratic transfer of power, and tarnishes US hopes of a smooth handover as it prepares to withdraw all US forces by late 2016.

BDST: 2141 HRS, JULY 02, 2014