The Iraqi army is still months away from staging a major offensive to retake ground lost to the Islamist State group and is regrouping after suffering battlefield defeats this year, US military officials said Thursday.

Iraqi security forces were now able to stage small-scale attacks against the Islamic State group but needed time to plan and train for a larger operation, even with the aid of US-led air strikes, one military official told reporters.

"It's well within their capability to do that (counter-attack), on the order of months, not years," said the official, speaking on condition of anonymity.

But he added: "It's not imminent."

Asked when the Iraqi army might be ready to launch an operation to push the Islamic State group out of the northern town of Mosul, the official said it could be up to a year.

Officials at the US military's Central Command headquarters acknowledged the pace of the bombing raids by American and allied warplanes has been limited by the Iraqi army's shortcomings, as it was not on the move and mainly in a defensive position.

There have been more than 600 strikes in Iraq and Syria since August 8, officials said, a much smaller number when compared to previous air campaigns in Libya or the 2003 US invasion of Iraq.

The scope of the air strikes also has hinged on how often the IS group moved in larger numbers in the open, leaving themselves open to attack.

Under the Shiite-led government of former prime minister Nuri al-Maliki, the Iraqi army had deteriorated in recent years with some capable senior officers replaced by political loyalists and equipment neglected, the official said.

US military advisors based in Baghdad and Arbil were working to shore up the Iraqi army, according to officials.

And for the first time, US officials left open the possibility advisor teams could eventually deploy to western Anbar province, where the Iraqi army has suffered a string of setbacks.

"I can't tell you when" advisers may operate out of Anbar, the official said. "There's been a lot of discussion and planning."

Such a move could put US forces at more risk, given the strength of the Islamic State group west of Baghdad, and open President Barack Obama up to criticism that he is escalating the American commitment despite a vow not to have "boots on the ground."

Obama's war strategy calls for helping to persuade Sunni tribes to confront the Islamic State militants, but officials said that effort -- led by Baghdad -- was only at a preliminary stage.

More than one tribe had joined the fight but "it's not a widespread tribal uprising," the official said.

Many Sunnis, who felt alienated by the previous Baghdad government, were "waiting to see which way the (Haider) Abadi government is going to go," he said.

- IS stalled in Kobane -

Officials said it was too soon to judge whether President Barack Obama's strategy to defeat the Islamic State group was succeeding because the war effort is in its early stages.

But commanders have said the initial goal of the air strikes was to stop the advance of the militants across Syria and Iraq, buying time to train and arm local forces to eventually roll them back.

In at least one battleground, in the mainly Kurdish town of Kobane in northern Syria, the American air strikes appear to have succeeded in helping halt the onslaught of the militants, officials said.

A weeks-long offensive by the jihadists around the border town has stalled and Kurdish fighters likely will be able to hold out indefinitely with the help of air raids, officials said.

The front lines between Islamic State militants and Kurdish forces have not moved for more than a week, despite a concerted push by the well-armed jihadists.

"If you look at what's happened over the last week and a half, really the line in Kobane hasn't really changed much," said a second official at Central Command.

"I think unless something happens out of the current paradigm of what ISIL (IS) is doing, I think the Kurdish defenders... are going to be able to hold."

The fate of Kobane has grabbed headlines and now carries crucial symbolic importance for both the IS group and the US-led coalition.

Officials said the Islamic State group had not given up its assault on the town, and would likely keep up its offensive.

But a failure to prevail in Kobane will present the militants with a propaganda problem, as it has painted itself with an aura of inevitability, the official added.

In Washington, Pentagon chief Chuck Hagel acknowledged "mixed" results in the war effort but said: "We believe that our strategy is working."