US officers are drafting plans to deploy American military advisers to Iraq's western Anbar province and to help arm Sunni tribes to fight Islamic State jihadists, officials said Friday.

"It's a plan that's being developed," a senior military officer said on condition of anonymity.

But before any advisers head to the volatile province, there was still more work to be done to ensure Sunni tribes were ready to confront the IS group and to coordinate the potential role of military advisers from other countries in the anti-IS coalition, the officer said.

About 600 US military advisers are currently based in Baghdad and in the northern city of Arbil.

But as IS has steadily rolled back the Iraqi army in the west, US and coalition officials have grown increasingly convinced of the need to station advisers in Anbar province to assist the Iraqi troops.

"We're going to have to help stiffen their resistance and provide some help outside of those two cities, Baghdad and Arbil, and specifically to help them in Anbar province," the officer told AFP.

But before expanding the US mission, the conditions would have to be favorable and there would be no hasty move to rush in an advisory team, the officer said.

"We're not going to be putting our guys in a situation where they could be overrun," the officer said.

His comments came a day after the US military's top officer, General Martin Dempsey, for the first time called for the deployment of advisers to Anbar, on the condition that the Iraqi government back the delivery of weapons to Sunni tribes in the area.

Dempsey "described a concept under development to provide advice and assistance to forces in other provinces, including Anbar," said Colonel Ed Thomas, spokesman for the general.

President Barack Obama has ruled out any combat role for American troops in Iraq, but Thomas said the advisers would not be entering into battle with the Iraqi security forces.

"To be clear, this is not a change in mission nor is it a combat role, as they will be operating in the same advisory role as the other locations," said Thomas.

Iraqi government support for Sunni tribes fighting IS militants was "necessary" and would represent "a first step" toward creating a proposed "national guard" for the Sunnis in the area, he added.

"From the beginning of the campaign, we have said that we would expand this type of support to the Iraqi government should they act in a manner that was representative of the security interests of all Iraqis," Thomas said in an email.

The Sunnis in Anbar have been reluctant to join forces with the Shiite-led Iraqi government, which they have accused of persecuting their community.

But US officials are hopeful that under new prime minister, Haidar al-Abadi, the Iraqi government will abandon sectarian politics and forge a dialogue with the Sunni tribes.

Defense Secretary Chuck Hagel agreed with Dempsey that advisers would be needed in Anbar, once the Sunni tribes were armed and other conditions were met, officials said.

Pentagon spokesman Rear Admiral John Kirby stressed that Iraqi government forces must reach out to Sunni tribes to "bring them into the fold."

Deploying advisers to Anbar is "an option that remains on the table, but we're not there yet," he said.