NATO's Secretary General confirmed on Thursday that the Alliance had requested a few thousand more troops in order for it to increase its presence in Afghanistan.

Jens Stoltenberg said in a brief statement, prior to a NATO defense ministers meeting, in Brussels that 15 nations had already "pledged additional contributions" to the Afghan Resolute Support Mission responsible for advising, training and assisting Afghan troops.

"Our military authorities have requested a few thousand more troops for the Mission in Afghanistan and today, I can confirm we will increase our presence in Afghanistan," he said ahead of the meeting.

Resolute Support is a NATO military advisory mission activated in 2015 after the International Security Assistance Force was disbanded, which signaled the end of NATO combat operations in Afghanistan.

Stoltenberg said the mission was intended to "help the Afghans fight and help them take full responsibility for the security in their own country."

The secretary general explained the increased support was especially needed in three areas: strengthening Afghan special operations forces, developing the Afghan air force and stepping up Afghan officers' leadership and education training initiatives.

"This is about adjusting, strengthening the train, assist and advise mission in Afghanistan," Stoltenberg added.

The Norwegian politician also hoped to "exchange views" with United States Secretary of Defense James Mattis in order to "assess the situation" and ensure "a sufficient number of troops in the NATO mission to continue to support the Afghans," and finally "pave the ground for a political solution."

Stoltenberg also said he did not "expect any specific troop numbers" on the US part.

Stoltenberg underscored there was a "close relationship between what is going on on the battlefield and the possibility of reaching a politically negotiated solution."

The NATO mission, supported by Spain, currently has 13,576 military advisors, according to the most recent NATO figures.