WASHINGTON (AFP) - President Barack Obama has approved sending up to 1,500 additional troops to Iraq to aid Baghdad government and Kurdish forces fighting the Islamic State (IS) group, roughly doubling the number of US troops in the country, the White House said Friday.

The 1,500 troops will include a group of advisers to help Iraqi forces plan operations and a group of trainers who will be deployed across the country, officials said, as Washington steps up the pressure on the IS militants.

Some of the advisors will be deployed to western Anbar province, where the Iraqi army has been forced to retreat from advancing IS militants, a defence official who spoke on condition of anonymity told AFP.

Some of the additional troops will begin to arrive in Iraq in the next several weeks, the official said.

"As a part of our strategy for strengthening partners on the ground, President Obama today authorised the deployment of up to 1,500 additional US military personnel in a non-combat role to train, advise, and assist Iraqi security forces, including Kurdish forces," a statement said.

Defense Secretary Chuck Hagel recommended the move to Obama based on a request from the Iraqi government and the assessment of US Central Command, which is overseeing the air war against the IS militants, the Pentagon said.

The deployment coincides "with the development of a coalition campaign plan to defend key areas and go on the offensive against the Islamic State of Iraq and the Levant," it said, referring to IS fighters who have grabbed large areas of Iraq and neighboring Syria.

The training will focus on 12 Iraqi brigades - nine Iraqi army and three Peshmerga brigades, the Pentagon said.

The training sites will be located in northern, western, and southern Iraq and "coalition partners will join US personnel at these locations to help build Iraqi capacity and capability," it added.