The Taliban insurgency will continue after coalition combat forces withdraw from Afghanistan in late 2014 but the Afghan government will survive, the ex-chief of the NATO-led force said Monday.

"Sometimes this comes as a surprise when I say this, that on January 1st, 2015 there's still going to be fighting in Afghanistan," General John Allen said in a speech to the Brookings Institution, a Washington think tank.

The NATO-led combat mission is scheduled to wind up on December 31, 2014 and be replaced by an 8,000-12,000-strong contingent tasked with training and advising Afghan army forces.

Allen, who left the post of commander of the NATO-led force called ISAF in February, said the insurrection in parts of the country will remain for a long time.

"There will be an insurgency in Afghanistan. The question really isn't whether there is a presence of an insurgency, the question is whether this insurgency is existential," Allen said.

He said he does not think it will be, mainly thanks to advances on the part of Afghan security forces.

"They turned out to be better than we thought and they turned out to be better than they thought," he said of the estimated 350,000-strong Afghan security forces.

Even specialized fields such as logistics, transportation, explosive ordnance disposal and aviation crewmanship "are beginning to emerge as viable occupational specialties," Allen said, although he added that much work remains to be done to build up Afghan forces.