* U.S., NATO say they would pull out without deal
* NATO chief says pullout would harm Afghan security
* Officials said aid would also be put at risk
By Adrian Croft and David Brunnstrom
BRUSSELS, Dec 3 (Reuters) - NATO leaders urged Afghan President Hamid Karzai on Tuesday to swiftly sign a security pact that would enable some U.S. troops to stay in Afghanistan after 2014, saying failure to do so could jeopardise security and foreign aid.
U.S. and NATO officials have warned that if Karzai does not sign the security deal with the United States promptly, both the United States and the alliance would have to withdraw all troops from Afghanistan by the end of 2014 and abandon plans to leave behind a smaller training and advisory force.
The NATO-led force now has some 84,000 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.
"My concern is that if we are not able to deploy a training mission to Afghanistan, it may have a negative impact on the security situation in Afghanistan and furthermore it may also have a negative impact on the provision of financial aid to Afghanistan," NATO Secretary-General Anders Fogh Rasmussen told reporters at a meeting of alliance foreign ministers.
He said he looked forward to Karzai's "timely signature" of the U.S. security pact.
Although terms of the Afghan-U.S. 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.
A senior diplomat at NATO said U.S. National Security Adviser Susan Rice had made clear on a recent visit to Kabul that Washington would begin planning a total pullout by the end of 2014 unless Karzai signed by the end of this year.
Other NATO officials have warned that, if all foreign troops left, it could put at risk up to $8 billion a year in foreign aid because donors would be reluctant to contribute to funding Afghan security forces if there were no foreign troops on the ground to see how the money was spent.
An assembly of Afghan elders, the Loya Jirga, last month endorsed the security pact intended to shape the U.S. military presence in the country beyond 2014. But Karzai said he might not sign it until after elections in April.
MINISTERS BACK CALL
Without the U.S.-Afghan accord, NATO has said it would not be able to finalise its own similar agreement with the Afghan government, meaning it would be forced to remove all of its troops by the end of 2014.
NATO foreign ministers discussed Afghanistan and stressed the need for the U.S. security pact to be signed "quickly, without delay", a NATO official said, and this message would be given to Afghan ministers joining the meeting on Wednesday.
"There does need to be an agreement in order for everything to function as I think Afghans would like it (to) after the end of 2014. I think ... we should concentrate on getting it done, let the U.S. and Afghanistan conclude it," British Foreign Secretary William Hague told reporters in Brussels.
A senior U.S. State Department official travelling to Brussels with Secretary of State John Kerry said the United States was pleased the Loya Jirga had approved the pact.
"We consider that the Loya Jirga represents the will of the Afghan people, and it's time to move on with it," the official said, speaking on condition of anonymity. (Additional reporting by Justyna Pawlak and Tom Koerkemeier; Editing by Mark Heinrich)