The long-term size of the Afghan security forces could be smaller than the 352,000 NATO has pledged to train and field by October 2012, NATO's secretary-general suggested Friday.

U.S. and NATO officials have been moving toward a decision on a revised target for Afghanistan's fledgling army and police, possibly leaving them much smaller than the target it says is needed in the short term to stabilise the country.

We have set the goal of reaching a level of 352,000 based on the assessment of the security situation in Afghanistan, but you asked me about the long-term perspective, what would be possible to finance and what would be the long-term sustainable size, and that might be a different figure, NATO Secretary-General Anders Fogh Rasmussen told a news conference.

Security forces of that size will go far beyond what is possible to finance by the Afghan government so we will need an engagement of the international community, he added during a visit to Lithuania. A final figure would depend on the security situation on the ground.

Details of funding pledges, which to a large extent will determine how large an Afghan force is possible, may not be announced until a NATO summit in Chicago in May.

The Afghan government, expected to require about $7 billion a year in outside help after most foreign troops go home by 2015, will not be able to pay for its own military for years.

European diplomats have said a plateau force of 250,000 might be more realistic. Some officials in Washington worry a smaller force will not be able to maintain Afghanistan security.

(Reporting by Nerijus Adomaitis; Editing by Peter Graff)