Kabul  - US three-star General David McKiernan took command of the 40-nation NATO-led military alliance in Afghanistan Tuesday.

The change of command took place in a ceremony at NATO's Headquarters in Kabul city attended by foreign ambassadors and senior Afghan officials including President Hamid Karzai.

Karzai thanked the outgoing NATO commander for his courage and service in stabilizing the country and fighting terrorism during his mission, but cautioned the new US commander that his job would not be easy in the face of mounting insurgency in the war-ravaged country.

"We will have a lot of days of working together, a lot of happy days, but also some sad days," Karzai said, adding, "We will lose lives, NATO soldiers will lose lives, but we must remain steadfast."

General McKiernan took command of the International Security Assistance Force (ISAF) from the retiring US four-star General Dan McNeill, whose 15-month-tenure saw the worst militancy since the deployment of foreign forces in Afghanistan.

Last year, the bloodiest since the 2001 ouster of the Taliban regime with more than 8,000 war-related deaths, also saw ISAF forces grow in strength by another 20,000 troops.

"While today marks a transition in commanders, the mission must continue without missing a beat," McKiernan said.

"Insurgents, foreign fighters, criminals and others who stand in the way of that mission will be dealt with," said McKiernan, who commanded the US land forces during the invasion of Iraq in 2003.

NATO took command of ISAF forces in 2003. The organization has more than 51,000 troops in Afghanistan from some 40 NATO and non-NATO countries, about half of them US soldiers.

The outgoing ISAF commander often said the military alliance was too small for its task to fight the resurgent Taliban.

"This is an under-resourced war and it needs more manoeuvre units, it needs more flying machines, it needs more intelligence, surveillance and reconnaissance apparatus," he said. (dpa)