baghdad iraqi government dismiss call u.s. secretary state rex tillerson iranian-backed paramilitary units help baghdad defeat islamic state end operations iraq speak meet sunday iraqi prime minister haider al-abadi saudi arabia king salman tillerson say time iraqi popular mobilisation force iranian advisers go home washington back baghdad islamic state concern iran use expand presence iraq syria expand influence region abadi show unwillingness meet tillerson demand party right interfere iraqi matter statement office read cite prime minister source close train arm iran iraqi popular mobilisation force often support iraqi government units fight militants effectively defeat july u.s.-backed offensive capture stronghold mosul pay iraqi government officially report prime minister arab sunni kurdish politicians describe militias de facto branch iranian revolutionary guard corp. iraq sunni neighbor include saudi arabia share washington concern shi ite power iran influence iraq population also predominantly shi ite office abadi shi ite say force authority iraqi government popular mobilisation iraqi patriots say statement unite state train tens thousands iraqi soldier course rebuild iraqi arm force 5,000 troop deploy country provide key air grind support offensive islamic state iraq dismiss u.s. call iranian-backed militias 'go home