KABUL, Afghanistan — NATO may keep fighting in Afghanistan past its 2014 target date for shifting authority to Afghan forces, the alliance’s top civilian in the country said today.

It was the latest indication that the U.S.-led military operation in Afghanistan will remain sizable well into the next decade, despite plans to draw down troops and transfer responsibility to the Afghan government.

NATO’s Mark Sedwill said the end of 2014 was not a deadline.

“It’s a goal,” he told reporters in the capital. “It’s realistic but not guaranteed.”

U.S. officials have said the handover will start early next year and run through the end of 2014 under a plan set for approval at a NATO summit this weekend in Lisbon, Portugal.

The 2014 option has been discussed for some time. But this week’s announcements mark the first time officials will outline concrete steps to meet the goal of transferring power in all 34 Afghan provinces within the next four years.

Sedwill said the number of NATO troops — currently at around 130,000 — may not be heavily reduced by that date, but the mission will shift to focus on training and advising Afghan troops.