NATO won’t be able to deploy its noncombat training and advisory mission in Afghanistan after next year unless President Hamid Karzai agrees to a bilateral security agreement with the U.S., the alliance’s secretary-general said Monday.

Mounting new pressure on the Afghan leader a day before NATO foreign ministers start a two-day meeting in Brussels, Anders Fogh Rasmussen said he hopes Karzai will sign the agreement needed for NATO to reach its legal framework for plans to assist Afghan forces after combat troops leave at the end of 2014 — which looms as a turning point for the Atlantic alliance as it phases down its largest-ever military mission.

“Let me be very clear: It is a prerequisite for our presence in Afghanistan beyond 2014 that an appropriate legal framework is in place,” Rasmussen told reporters at NATO headquarters after meeting with new Norwegian Prime Minister Erna Solberg. Without it, “it will not be possible to deploy a train, advise (and) assist mission to Afghanistan after 2014.”

Karzai has refused to sign a bilateral security agreement with the Obama administration despite strong support from a key Afghan national assembly, deferring a decision to his successor after elections in April. Alliance military chiefs and diplomats say they need time to plan, and the U.S. has threatened to make plans for a complete pullout if a bilateral deal isn’t signed by the end of December.

U.S. Ambassador to NATO Douglas Lute told reporters Monday that the deal is an important “first link in the chain” that could ultimately bring more than $8 billion for Afghan security forces and development assistance.

The ministers’ meeting is shaping up as an opportunity for alliance members to play up successes in Afghanistan in the face of continued instability there and low public support in the U.S. and Europe about the nearly 12-year NATO mission.

Following the Sept. 11 attacks, the U.S. led an international intervention that toppled the Taliban regime in Afghanistan and has taken the lion’s share of responsibility in NATO’s multi-nation International Security Assistance Force since then.