Kerry hails 'historic' Afghan elections

US Secretary of State John Kerry says he hopes weekend presidential elections in Afghanistan will mark a "historic" democratic transition in the war-torn country.

With the US still trying to firm its post-2014 military presence in Afghanistan after a draw-down later this year, Kerry said Saturday's vote marked a "pivotal moment after more than a decade of sacrifice and struggle."

"When millions of Afghan men and women go to the polls on April 5 to choose a new president it could mark Afghanistan's first democratic transition of power, and we all have a stake in seeing that milestone achieved," Kerry said on Wednesday in a statement.

Afghans are to vote on a successor to outgoing leader Hamid Karzai, who has been at loggerheads with the United States over his refusal to endorse a Bilateral Security Agreement governing the terms of a US military deployment in Afghanistan after this year.

Kerry congratulated Afghans for organising elections which had been "Afghan-owned from the start."

"The peaceful handover of power will be just as important as the progress achieved over the past decade in building a stronger, more secure and prosperous Afghanistan," added Kerry, who has twice visited Kabul in the past year since taking over as Secretary of State.

"The United States is ready to work with the next president, and we look forward to an enduring partnership with the Afghan people, consistent with our shared democratic values and interests," Kerry added.

Kerry made no mention over the spat with Karzai over the BSA, which made provisions for a residual force of around 10,000 US troops to remain in Afghanistan until the end of 2016 on a mission to train Afghan forces and hunt Al-Qaeda.

Kerry has previously said Washington hopes to ink the BSA deal with Karzai's successor. President Barack Obama has ordered US forces to plan for a full withdrawal of troops later this year if no deal is agreed.