NATO head Anders Fogh Rasmussen welcomed Afghan President Hamid Karzai Tuesday as the alliance prepares for a difficult withdrawal from Afghanistan in 2014 after years of fighting the Taliban.

NATO forces in Afghanistan are steadily "moving from combat to support," Rasmussen said, promising that the alliance would stand by the country through to 2014 and beyond, when it will take up a military training mission.

Afghanistan "will definitely be able to provide for the security of the Afghan people," Karzai said in reply at NATO HQ in Brussels.

"I am glad that the ... transition is going well," he said.

Karzai is due to meet later Tuesday with US Secretary of State John Kerry, said Belgian Foreign Minister Didier Reynders who is providing the facilities for the meeting.

Kerry, in Brussels for a NATO foreign ministers gathering, is also due to meet the head of the Pakistan armed forces, Ashfaq Kayani.

The secretary of state said earlier that he would bring together the Afghan and Pakistan officials as part of efforts to buttress security in Afghanistan and the region.

Relations between Islamabad and Kabul have been strained for many years and Karzai has accused Pakistan of aiding the Taliban, who seek refuge along their rugged border.

Kerry said Monday that 2013 was a "critical" transition year for Afghanistan and Wednesday's talks would about "how we can advance this process in the simplest, most cooperative, most cogent way."