US sends 400 more troops to Iraq ahead of Mosul push

More than 400 additional US troops have deployed to Iraq in recent days, a defence official said on Thursday, as local forces prepared for an assault on Mosul, the Islamic State (IS) group's last major Iraqi stronghold.

Colonel John Dorrian, a spokesman for the US-led coalition that has been attacking IS in Iraq and Syria for the last two years, said the number of US troops in country had increased from about 4,000 a week ago to 4,460 today.

The deployments were authorised earlier this year.

Dorrian did not say what the troops would be doing, but their arrival comes as Iraqi security forces continue "shaping operations" around Mosul, Iraq's second-largest city.

Much of the work is focused on an airfield near the town of Qayyarah, which will provide a staging area for Iraqi forces pushing towards the northern city. 

Lieutenant General Stephen Townsend, the new commander of the US-led coalition, told the Wall Street Journal late Wednesday that the assault could begin within the next month. 

Dorrian, however, said it was the Iraqis who would determine any timeline.

General Joe Votel, the head of the US military's Central Command, last week said coalition-backed Iraqi forces can retake Mosul by the end of the year. 

Iraqi security forces from the south and Kurdish Peshmerga forces from the north are expected to conduct the push from multiple directions. 

Mosul had an estimated population of two million before IS took over in a June 2014 offensive that sparked large-scale displacement.

Accurate numbers for the population remaining in the city are hard to come by, but the United Nations and other officials have said as many as one million civilians may still be living under IS rule in the area.

Dorrian said an estimated 3,000 to 4,500 IS militants are in Mosul, though he noted it was hard to say how many were "hardcore," compared with "people that are not as committed to the fight".