The US commander of international forces in Afghanistan has hailed the achievements of 13 years of fighting against the Taliban, as NATO formally ended its war at a ceremony in Kabul.

General John Campbell told assembled NATO soldiers that together, they had lifted the Afghan people out of despair and given them hope for the future - making Afghanistan stronger and both countries safer.

On January 1, the US-led International Security Assistance Force (ISAF) combat mission, which has suffered 3,485 military deaths since 2001, will be replaced by a NATO training and support mission.

The ceremony was arranged in secret because the threat of Taliban strikes in the Afghan capital, which has been hit by repeated suicide bombings and gun attacks over recent years.

The US President says the longest war in the country's history is coming to a responsible conclusion.

Obama has honoured the more than 2,200 US troops who have died in Afghanistan since the war started 13 years ago.

From a peak 140,000 troops in 2010, the US and NATO plan to leave 13,500 behind.