General Martin Dempsey, the top US military officer, has arrived in Baghdad on an unannounced visit to meet US commanders preparing to expand American assistance to Iraqi and Kurdish forces battling the Islamic State of Iraq and the Levant (ISIL) group.

It was Dempsey's first trip to Iraq since US President Barack Obama, alarmed by ISIL advances, ordered non-combatant American forces back into the country this summer, less than three years after withdrawing US troops from Iraq.

The US began carrying out air strikes in August.

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"I want to get a sense from our side about how our contribution is going," Dempsey, chairman of the US military's Joint Chiefs of Staff, told the Reuters news agency shortly before landing in Baghdad.

"I want to hear from those actually doing the lifting that they've the resources they need and the proper guidance to use those resources."

Last week, Obama authorised sending up to 1,500 more forces to Iraq, roughly doubling the planned US troop presence as the United States expands its advisory mission and starts training Iraqi and Kurdish forces.

Dempsey was due to meet US officials overseeing the effort, including Kuwait-based task force commander Lieutenant General James Terry, as well as Iraqi officials.

"This will work best if we're enabling [Iraq's] plan," Dempsey, who last visited Iraq in 2012, said.

Gains against ISIL

Dempsey's visit comes in the wake of Iraqi battlefield advances touted by US officials, including retaking areas around the country's biggest refinery near the city of Baiji.

Kurdish forces pushed ISIL out of the town of Zumar in northern Iraq and US air strikes hit a gathering of ISIL battlefield commanders near Mosul just over a week ago.

Still, ISIL remains defiant, and has dug into key Iraqi cities, including Mosul.

An audio message purported to be from the group's leader this week urged supporters in Saudi Arabia to take the fight to the rulers of the kingdom, which has joined the US-led coalition in mounting air strikes against ISIL in Syria.

About 1,400 US troops are now on the ground, just below the previous limit of 1,600 troops. The new authorisation from Obama gives the US military the ability to deploy up to 3,100 troops.

Source: Reuters