BRUSSELS - Nato would have to pull all its troops out of Afghanistan by the end of 2014 if Afghan President Hamid Karzai does not sign a security pact with the United States, alliance chief Anders Fogh Rasmussen said.

An assembly of Afghan elders, the Loya Jirga, last month endorsed the security pact intended to shape the US military presence in the country beyond 2014. But Karzai said he might not sign it until after elections in April.

The Nato-led force currently has around 80,000 troops in Afghanistan, the majority American. Nato is winding down combat operations, handing responsibility for fighting Taliban insurgents to the Afghans, before most foreign combat forces pull out by the end of 2014.

Nato plans to leave a training mission, expected to number 8,000 to 12,000 soldiers, in Afghanistan after 2014.

The United States has already warned it could withdraw all its forces by the end of next year, the so-called “zero option”, if Karzai does not sign the pact.

Without the U.S.-Afghan accord, Nato will not be able to finalize its own agreement with the Afghan government setting the terms for troops from other Nato and partner nations to remain in Afghanistan after 2014, Rasmussen told reporters. “In that case, we don’t have a proper legal framework in place and it will not be possible to deploy a ‘train, advise, assist’ mission to Afghanistan after 2014,” Rasmussen said.

He voiced hope Karzai would follow the advice of the Loya Jirga and sign.

The agreement that Nato needs with Afghanistan is modeled on the proposed US pact and, in any case, Washington is expected to supply most of the forces for the post-2014 Nato mission, so without the United States, the mission is unlikely to be feasible. Although terms of the Afghan-US pact were settled after a year of wrangling, Karzai has since added conditions including the release of all Afghan prisoners from Guantanamo Bay in Cuba and an end to military operations involving Afghan homes.

Nato foreign ministers meet in Brussels on Tuesday and Wednesday to discuss Afghanistan. The delay in signing the US-Afghan security pact is causing mounting frustration among Nato diplomats because it is holding up detailed military planning for the post-2014 mission.

NATO officials and diplomats warned privately of dire consequences for Afghanistan, including threats to up to $8 billion a year in aid, if Karzai failed to sign the US pact.

A senior diplomat at Nato said US National Security Adviser Susan Rice had made clear on a recent visit to Kabul that Washington would begin planning to pull out all its troops by the end of 2014 unless Karzai signed by the end of this year.

Foreign donors are required to provide the bulk of the $4 billion a year needed to finance the Afghan security forces.

Withdrawal of all foreign troops could jeopardize that foreign funding as well as around $4 billion a year in civilian aid, the diplomat, speaking on condition of anonymity, said.

“We are concerned, without those eyes and ears on the ground, that the $4 billion a year (in security assistance) will be difficult to appropriate across our capitals because there will simply be less confidence that the money is going to go where it is intended to go,” he said.

According to AFP, officials say the focus of the two-day meeting in Brussels is to build on NATO’s active military role since the early 1990s, from the Balkans to Afghanistan and Libya, safeguarding gains in inter-operability and capability at a time when defence budgets are under strain.

The aim is a Nato which remains relevant and effective in a changing world where the challenges are as much military as political and economic, threatening to boil over into conflict and social upheaval.

“We have got to ensure that we sustain Nato’s military edge,” a senior US official said.

“In the context of extreme budgetary constraints ... it is incumbent on us all to do more with (the money) that we have.”

The 28 allies, plus Nato’s partners and sometimes adversaries such as Russia, will review issues such as how to destroy Syria’s chemical weapons arsenal.

Missile defence, a hugely sensitive issue for Moscow, is on the agenda given US and European concerns of a threat from Iran despite the recent signing of an initial deal on its contested nuclear programme.

Relations with Ukraine and Georgia provide another difficult issue for Russian Foreign Minister Sergei Lavrov and his US counterpart Secretary of State John Kerry as NATO seeks to maintain and boost ties with former Soviet states.

Continued and growing protests in Ukraine after the government ditched a planned association accord with the EU are likely to test ties.

Following the NATO meeting, Kerry will travel to Moldova which did sign up with Brussels last week despite intense Russian pressure not to.

“We are making this brief stop to demonstrate US support for the important choice that Moldova made,” the US official said.