Speaking to The Daily Beast, Stephen Townsend said that despite Iraqi commanders telling local media that the Mosul assault was going ahead without break, the reality is that they have paused over the last week to resupply.
"People need to rest. They need to assess how things are going because they are not going as fast as we thought," the US commander said, adding that the US had forewarned their Iraqi partners of this.
According to Townsend, the misleading reports given to reporters by Iraqi military sources is due to an unwillingness on their part to admit mistakes and constraints. He added that this is one of the biggest challenges of working with the Iraqi forces, as the sensitivities of the Iraqi military sometimes prevent American commanders from being completely honest with US media outlets.
The commander said that Iraqi forces are facing challenges in dealing with armoured car bombs, which they are learning to deal with without proper training.
"Quite honestly, I don't think we trained them [Iraqi soldiers] to do that. They are learning to do it in combat," Townsend said.
Despite allegations of abuses levelled against them, Townsend heaped praise on the Iran-back militias, known as the Hashd al-Shaabi [Popular Mobilisation Forces].
"Before I got here, I read all kinds of things about the PMF, and I got here and I haven't observed that behaviour. We're not having allegations of bad behaviour or misconduct," he said.
"The PMF did advance more rapidly than we expected and they've done a good job," he added, referring to their advance towards the IS stronghold of Tal Afar, west of Mosul.
The US commander's praise for the militias came just a day before a new Iraqi law came into force legalising the militia groups. This places them under the umbrella of Iraq's armed forces, however makes them directly answerable to Prime Minister Haider al-Abadi.
Iraqi forces backed by a US-led coalition launched an operation on October 17 to retake Mosul from the IS group.
In Syria, meanwhile, US-backed rebel forces are advancing on Raqqa with the aim of isolating the city and cutting logistics routes, ahead of a siege that is expected to begin in 2017.
These two cities are the last major strongholds of the IS group, which was defeated earlier this year in the Iraqi city of Fallujah.