A joint Iraqi-Kurdish military force of up to 25,000 fighters is being prepared to retake the Iraqi city of Mosul from Islamic State, a US official said.
According to the senior military official, the operation to recapture the northern city will probably take place in April or May, BBC reported.
Iraq's second largest city is currently being held by 1,000 to 2,000 IS militants, the official added. Mosul was home to more than a million people before it fell to IS last June.
The unnamed official told reporters that no decision had been made on whether a small group of US military advisers would be needed on the ground to direct air support.
All of the fighters in the force will have gone through US training by the time of the operation, the official added.
He said the operation would be needed by May, otherwise it would be compromised by the summer heat, although he added that it could be delayed if the Iraqi forces were not ready.
Earlier in the week, Iraq's Prime Minister Haider al-Abadi confirmed that his forces were "planning an offensive on Mosul."
Abadi hoped Mosul would be liberated in a few months' time, with a minimum of casualties.
Fighters from the Kurdish Popular Protection Units (YPG) and three other groups have advanced steadily into IS-held territory since securing control of Kobane on January 26.
The YPG and its allies are also now in control of about 35km of the motorway connecting the cities of Aleppo and Hassakeh.
