BERLIN, March 12 (Reuters) - Chancellor Angela Merkel paid an unexpected visit to German troops serving in Afghanistan on Monday, a day after an American soldier killed 16 civilians in a shooting spree that has further strained troubled ties between Kabul and the NATO-led mission.
Merkel, who visited German troops based near Mazar-e-Sharif in northern Afghanistan, also spoke by telephone with Afghan President Hamid Karzai and expressed German condolences for the shootings that took place in villages in Kandahar province.
Branding the killings a "terrible deed", Merkel said NATO's International Security Assistance Force (ISAF) would do all it could to clarify exactly what happened, her spokesman Steffen Seibert said.
Merkel's trip was organised before the killings and she made no adjustments to her itinerary because of the incident, though bad weather forced her to ditch plans to visit German troops at another base at Kundus.
Calls for U.S. and NATO forces to leave Afghanistan are expected to rise after the deaths, which included many women and children. The incident may also force Karzai to harden his stand in talks with Washington on a new Strategic Partnership Agreement that would allow U.S. advisers to remain in the country after the end of the ISAF mission.
Commenting on the planned withdrawal of NATO troops from Afghanistan in 2014, Merkel urged the Karzai administration to promote the political reconciliation process with insurgents, saying there had been progress but that much more was needed.
"For that reason I cannot say we will manage this by 2013-2014. The will is there, we want to succeed and we will work on this," she was quoted as saying.
Asked if Merkel was signalling doubts over plans to pull out troops by the end of 2014 and hand responsibility for security entirely to Afghan forces, a German official told Reuters: "The chancellor is not calling into question the withdrawal plan."
Germany is the third largest contributor of troops to ISAF, with over 5,000 soldiers.
Merkel last visited Afghanistan in 2010. (Reporting by Andreas Rinke and Gareth Jones; Editing by Toby Chopra)