baghdad unite state send troop iraq put close front line battle advise iraqi force war islamic state militants u.s. defense officials say monday washington deploy 200 additional troop mostly advisers iraqi troop advance towards mosul large iraqi city still islamic state control see iraqis will fight gain grind let make sure provide support u.s. president barack obama say interview cbs news expectation end year create condition whereby mosul eventually fall obama say unite state also authorize use apache attack helicopters help iraqis provide quick air support precision fire advisers accompany iraqi units 2,500 troop move close front line battle advisers limit large divisions 10,000 troop locate back battlefield change allow offer quick advice iraqi troop try retake mosul likely face stiff resistance entrench enemy could also leave u.s. advisers vulnerable enemy mortar artillery put americans close action u.s. defense secretary ash carter say whole purpose able help force respond agile way decision enlarge u.s. military force make close concert iraqi authorities say carter meet u.s. commanders iraqi officials include prime minister haider al-abadi visit baghdad iraq engulf political crisis anti-corruption reform cripple state institutions threaten slow campaign militants increase raise authorize troop level iraq 4,087 include special operations personnel logistics workers troop temporary rotations pentagon also provide 415 million kurdish peshmerga military units play important role push back islamic state northern iraq part fund likely spend basics like food say lieutenant general sean macfarland head u.s.-led coalition battle islamic state right peshmerga get enough calories keep field macfarland say increase late move unite state invade iraq 2003 overthrow saddam hussein step campaign hardline sunni jihadists since december iraqi force train u.s. military back coalition air strike take back territory islamic state seize swathe iraq syria 2014. u.s. troop already iraq shift establish logistics iraqi force move towards mosul carter say include supply line particularly important mosul 400 km 250 miles north baghdad new u.s. advisers make bulk new troop army special force 100 advisers iraq rest troop announce monday include support crew apaches security force protect advisers unite state also deploy additional long-range rocket artillery unit support iraqi grind force battle mosul carter say two batteries already place iraq officials rule possibility last success might require u.s. commitments take us way come back another discussion ask need mcfarland say u.s. send troop iraq tackle islamic state