NATO Secretary General Jens Stoltenberg says the troops were needed to train local forces and not for combat operations.
NATO is assessing a request from the alliance's military authorities to send more troops to Afghanistan and will make a decision within weeks, Secretary General Jens Stoltenberg said on Wednesday.
Stoltenberg said that the request was "about a few thousand" more troops at a time of a worsening security situation in Afghanistan, territorial gains by Taliban and military and civilian casualties.
"We are now assessing that request. We will make decisions on the scale and scope of the mission within weeks but this is not about returning back to a combat operation in Afghanistan," he said after meeting the British Prime Minister Theresa May.
NATO already has some 13,450 troops in Afghanistan, including about 6,900 US military personnel, who are training the Afghan armed forces to eventually take over the country's defence and security.
Almost 16 years since the US tried to topple Afghanistan's Taliban, the West remains entangled in an effort to stabilise a country facing resurgent rebels.
Facing public fatigue in the long-running conflict, NATO has sought to progressively reduce its presence in the country by building up the country's armed forces, notably creating an Afghan air force.
However, loss of territory to Taliban and Daesh militants, a rise in civilian casualties and a fall in the number of Afghan security forces have led the US administration under President Donald Trump to review Afghanistan policy.
Over the past 18 months, Taliban insurgents have twice succeeded in seizing the northern town centre of Kunduz for brief periods and the latest fighting underscores the challenge Afghan forces face to quell the insurgency.
According to the United Nations, 583,000 people fled their homes due to conflict in 2016, the highest number of displacements since records began in 2008.
In April US National Security Advisor HR McMaster visited Kabul to assess the situation, days after the US military dropped one of the largest conventional bombs ever used in combat in eastern Afghanistan.
"I strongly believe that the best answer we have to terrorism, the best weapon against terrorism, is to train local forces to fight terrorism, to stabilise their own country," Stoltenberg said.