KABUL: The incoming No 2 American commander in Afghanistan said Saturday that his immediate focus is on supporting upcoming Afghan elections, not on the possibility of US troops remaining after the Nato-led combat mission ends.

At a ceremony in Kabul, Lt Gen. Mark Milley handed over International Security Assistance Force (Isaf) Joint Command to Lt Gen Joseph Anderson, the last such handover, as the mandate for the US-led Isaf expires at the end of 2014.

Afghan President Hamid Karzai has delayed signing a deal that would allow some a small number of troops to stay in the country after Nato combat troops withdraw, creating friction with Washington.

The military has been pushing to keep up to 10,000 US troops in Afghanistan after 2014, but the White House says President Barack Obama won't leave any American forces in Afghanistan unless Karzai signs.

Gen Joseph Dunford, the US's top commander in Afghanistan, noted ''the difficult political challenges,'' saying in remarks at the change of command ceremony that the coalition's commitment to Afghanistan's success is ''unwavering.''

Anderson, who will run the day-to-day coalition campaign, acknowledged that the uncertainty around the security deal gives him a ''little bit of pause'' but is ultimately a ''longer term issue.''

''Right now the immediacy is supporting the elections and earlier fighting season and getting through all that through the summer,'' he said. ''Then based on whatever number we have to deal with, we will adjust.'' ''We'll deal with each step along the way,'' he added.

Afghanistan's presidential election is slated for April 5, and there are fears the Taliban will ramp up violence to sow fear in an attempt to disrupt voting.