washington unite state send 3,500 additional u.s. troop afghanistan u.s. officials say wednesday figure broadly line expectations unite state boost support afghan military disclosure officials speak condition anonymity come defense secretary jim mattis chairman joint chiefs staff marine general joseph dunford hold close door brief members congress president donald trump regional strategy pentagon say would comment additional troop number mattis make announcement confirm would bring total number u.s. troop afghanistan 14,500. months-long review afghanistan policy trump commit unite state last week open-ended conflict country promise stepped-up campaign taliban insurgents last week mattis say sign order send additional troop afghanistan specify size force say first need brief congress u.s. officials months tell reuters trump give mattis authority send 4,000 additional troop afghanistan u.s. presence afghanistan peak 100,000 troop 2011 washington domestic political pressure draw costly operation u.s. officials tell reuters question benefit send troop afghanistan politically palatable number would enough turn tide much less create stability security date 2,300 americans kill 17,000 wound afghanistan u.s. send 3,500 additional troop afghanistan