The additional troops, most of them American, will help train and advise local Afghan forces who have struggled to hold Taliban and Islamic State extremists at bay while suffering heavy casualties.
"Our allies and partners have committed to sending more troops," NATO chief Jens Stoltenberg said Thursday.
"Today we will review progress and discuss what more needs to be done, to enhance Afghan combat capabilities in the fight against international terrorism, and to establish the environment to achieve Afghanistan’s ultimate objective of peace and reconciliation."
NATO leaders are optimistic that 2018 could see Afghan forces start to gain momentum against the Taliban, thanks to renewed training efforts, a growing air force and thousands of extra Afghan commandos.
Plus US President Donald Trump has given American forces greater leeway in how and when they can hit the Taliban, and Afghan forces are increasingly going on the offensive.
Immediately following the summit, US Defence Secretary Jim Mattis will host a separate meeting with partners from the coalition fighting the Islamic State group in the Middle East, where the jihadists continue to lose territory.
Mattis said coalition partners are looking to the United States for a clear plan about what follows the physical defeat of IS.
"Maybe three-quarters of the questions I am getting asked now is (about) going forward. It's not about are we going to be able to stop ISIS, are we going to be able to overcome ISIS. They are now saying: 'What's next? How is it looking?'" Mattis told reporters this week using another acronym for the group.
Following back-to-back losses, including of their Syrian and Iraqi strongholds of Raqa and Mosul, IS fighters are down to defending their last holdouts along the Euphrates River valley.
America's military involvement in Syria has until now been focused solely on fighting IS, but with the jihadists on the ropes, Washington must articulate its longer-term interests and what role, if any, US forces will play in Syria.
A French source said allies were keen to hear what Mattis had to say about the role of Iran -- a key supporter of Syrian President Bashar al-Assad -- following Trump's tough rhetoric against Tehran.
"We are wondering how the speeches by top US officials on the need to push back the Iranian presence in the region is going to manifest itself in real terms in the military strategy," the source said.