Two American soldiers were killed in Wednesday's suicide car bombing in southern Kandahar province, Pentagon officials confirmed.
Local officials also confirmed that one Afghan civilian had also been wounded in the bombing.
A suicide bomber targeted a US troops convoy close to the airport at about 12 noon on Wednesday.
The US said the convoy of troops had been on a routine train, advise and assist mission when attacked.
The Taliban has claimed responsibility for the incident.
"I can confirm that two US service members were killed in action in Kandahar, Afghanistan, when their convoy came under attack," said Pentagon spokesman Capt. Jeff Davis to Reuters.
"US Forces Afghanistan will provide additional information as it becomes available."
This came after Resolute Support, the NATO-led mission in Afghanistan, confirmed the suicide bomber had targeted a NATO convoy.
The latest deaths raise the number of US troops killed in action in Afghanistan so far this year to nine, matching the total for all of 2016.
There are 8,400 US troops in Afghanistan, where they train and advise the Afghan military in the fight against the Taliban and Daesh.