A soldier serving with the International Security Assistance Force in Afghanistan was shot dead by a man in Afghan army uniform, the latest in a series of "insider" attacks, the alliance said on Tuesday.
More than 60 ISAF troops were killed in 2011 in a surge of insider attacks that have shaken relations between the alliance and Afghanistan as the US-led troops try to train up the local army and police to battle Taliban militants.
The attack on Monday came as US President Barack Obama prepares to host Afghan President Hamid Karzai at the White House later in the week for talks focused on the long-term security compact between the two countries.
"An individual wearing an Afghan National Army uniform turned his weapon against International Security Assistance Force service members in southern Afghanistan on Monday, killing one," ISAF said in a statement today.
It gave no further details of the incident, adding it was ISAF policy for the dead soldier's home nation to issue an identification.
Taliban militants often claim such insider attacks are planned strikes by its supporters, but ISAF and Afghan officials say that many are due to personal grudges.
The threat has become so serious that international soldiers working alongside Afghan security forces are often looked over by so-called "guardian angel" troops on duty to provide protection.
In one incident in November, an ISAF soldier fighting insurgents in the Nad Ali district of Helmand province was shot dead after a "verbal argument" at a joint camp.
Last month, a female police officer killed a US adviser in Kabul's police headquarters - the first insider attack by a woman.
Scores more Afghans have also been killed in insider attacks, with four policemen killed 10 days ago when a colleague let in attackers as officers slept at a post in the southern province of Uruzgan.
The policeman who aided the attack then fled with the Taliban militants.
There are presently around 100,000 US-led troops fighting alongside Afghan security forces against the Taliban-led insurgency that has been raging since a US-led invasion toppled the Islamist regime in late 2001.
NATO combat forces are scheduled to withdraw from Afghanistan by the end of 2014.