WASHINGTON - US President Barack Obama will meet with Afghan President Hamid Karzai in Chicago on Sunday, when the NATO summit there is due to start, a top White House official said on Thursday.

"Obviously it is an important meeting because a central focus of the NATO summit will be on Afghanistan and on Afghanistan's future," said Obama's National Security Advisor Tom Donilon at a White House briefing, referring to the meeting between the two.

Obama met with Karzai earlier this month during his surprise visit to Afghanistan, where they signed the US-Afghanistan Strategic Partnership Agreement.

Donilon also confirmed that so far there is no plan for a bilateral meeting between Obama and Pakistani President Asif Ali Zardari even though the latter was also invited to attend the summit.

It is still unclear whether the United States and Pakistan can sign an agreement for the reopening of a key NATO supply route before the NATO summit kicks off on Sunday.

The supply line was cut off by the Pakistani government following a deadly NATO airstrike on two Pakistani border checkpoints in November last year, which killed 24 Pakistani soldiers.

The decade-old war in Afghanistan will dominate the NATO summit in Chicago slated for May 20-21. The summit is expected to iron out details of an exit strategy from the war-torn country, under which Afghan forces are expected to take the security lead by the end of 2014 after most American and NATO combat troops leave.