US Secretary of Defence Ashton Carter arrived in Iraq's autonomous region of Kurdistan on Sunday to review the ongoing military offensive to retake the jihadist bastion of Mosul.
As the Pentagon chief went into talks with Kurdish leader Massud Barzani, US officials said Kurdish peshmerga forces had almost reached their goals in the week-old offensive.
The battle plan is for the peshmerga forces to stop along a line at an average of 20 kilometres (12 miles) outside of the city of Mosul, the Islamic State group's last major stronghold in Iraq.
"They are pretty much there," a US military official said Saturday when Carter was holding meetings in Baghdad.
Elite federal forces are then expected to take the lead and breach into the city proper, where more than a million civilians are still believed to be living.
That peshmerga line of control, mostly on the northern and eastern fronts, "will be solidified in the next day or two," the official said.
The United States leads a 60-nation coalition -- which also includes Britain and France -- that has provided key support in the form of thousands of air strikes, training to Iraqi forces and advisers on the ground.
Kurdish forces are currently engaged in a huge push around the IS-held town of Bashiqa, northeast of Mosul.
They gained significant ground on the eastern front in the first days of the offensive, which was launched on October 17.
In Baghdad, Carter praised the peshmerga and "the way their efforts are completely coordinated with the ISF (Iraqi securitry forces)."
The coordination between Baghdad and Arbil, at odds over Kurdish independence and oil revenue, had been one of the key question marks ahead of the offensive.
Lieutenant General Stephen Townsend, commander of the US-led coalition, noted on Saturday that, while progress in the offensive was satisfactory, jihadist resistance was stiff.
"The resistance is about as broad as expected," he said in Baghdad.
"It's pretty significant, we are talking about enemy indirect fire, multiple IEDs (improvised explosive devices), multiple VBIED (vehicle-borne IEDs) each day, even some anti-tank guided missiles, so it's been very tough fighting, snipers, machineguns," he said.
US military officials have revised their estimate slightly upward for the number of IS fighters involved int he Mosul theatre.
They believe the IS group is defending its stronghold of Mosul, where the "caliphate" was proclaimed in June 2014, with 3,000 to 5,000 fighters inside the city and 1,000 to 2,000 spread out on the outskirts.
A French government official told AFP the breach into Mosul, which could mark the beginning of a phase of fierce street battles with IS, could still be a month away.