By Jessica Donati and Hamid Shalizi
KABUL (Reuters) - NATO Secretary General Jens Stoltenberg on Thursday reaffirmed the alliance's commitment to stabilizing Afghanistan and ensuring that the gains made are preserved after the foreign combat mission ends in 2014.
Afghan security forces have been largely left to fight the Taliban on their own this year, in their first real test since the militant Islamists were ousted from power in 2001 by U.S.-led forces.
Government forces hold cities and towns and district centers have also largely held out but police and army casualties have been described as "unsustainable" and the Taliban have regained territory in strategic provinces where they have resumed the role of de facto government.
"Much has been sacrificed over many years to give Afghanistan a chance to succeed," Stoltenberg told troops at Camp Morehead in Wardak province, where U.S. special forces have been training their Afghan counterparts to take over.
"We cannot and we will not allow these gains to be lost," he said, according to a NATO statement.
More than 4,600 Afghan troops have been killed in the war against the Taliban this year, a 6.5 percent increase over last year.
Underscoring the growing violence, officials in the eastern province of Paktia accused the Taliban of executing eight civilians. The militants claimed responsibility, saying the men who were shot were members of the security forces.
President Ashraf Ghani told a joint news conference with Stoltenberg that NATO's investment in the country's 350,000 strong security force had been a success and that he looked forward to working with the alliance.
"After December 31, 2014, only Afghan forces will be responsible for the use of weapons, this however does not mean an end to cooperation with NATO, but the start of a new process," he told reporters.
A contingent of about 10,000 foreign troops, most of them American, will stay in Afghanistan after the end of the year to train and support Afghan forces. About 1,800 Americans will be involved in counter-terrorism operations.
While aiming to maintain close ties with NATO and its Western members, Ghani is also looking to bolster alliances in Asia.
His first official visit after taking office in September was to China, which pledged $327 million to help ensure Afghanistan's stability through 2017 - more than it has contributed since the U.S. led invasion.
China is connected to Afghanistan by a narrow, almost impassable mountain corridor and is concerned instability along the Afghan border with Pakistan could spur attacks by militant separates in its western Xinjiang region.
(Additional reporting by Sultan Ahmad in Gardez; Editing by Robert Birsel)