"It may be penny-wise but would be pound-foolish to put at risk the hard-fought gains we, our coalition partners, and the Afghans have achieved rather than support an Afghan security force that is right-sized to provide security to the Afghan people and prevent a Taliban return to power," Levin said.
Miller said it will cost more than $4 billion annually to maintain a 352,000-troop Afghan security force. NATO has pegged the figure at least $8 billion a year.
U.S. military and Afghan officials are in talks about how large the indigenous security and police force should be beyond 2014. Allen said it will remain at 352,000 "for at least a year" after most American troops are gone on Dec. 31, 2014.
Though U.S. officials and lawmakers have said some U.S. special forces and support troops will remain for counterterrorism missions, Allen made clear in more than six hours of testimony this week that Afghan troops are increasingly in the lead.
That is why officials believe Afghanistan will need 352,000 troops to secure operational gains made since 2009. But beyond 2015, he said, U.S. and Afghan officials believe the indigenous force will shrink to around 230,000.