US military leaders are weighing whether to request additional coalition troops to help local forces fighting the Islamic State group in Iraq, but no decisions have been made, a military official said Thursday.

"We're constantly looking to see if we're right-sized," said British Army Major General Doug Chalmers, adding that troop levels and additional capabilities formed part of an "ongoing dialogue."

The comments from Chalmers, who is deputy commander for support in the US-led coalition against the IS group in Iraq and Syria, followed a Washington Post story saying generals want to ask President Barack Obama for additional troops and equipment to help consolidate gains against the jihadists.

Chalmers declined to provide specifics but said additional capabilities could come in the form of logistics, equipment, air support and surveillance.

When asked how many additional troops might be requested, he said: "I can guarantee you, it's not (in) the thousands."

The Post said Lieutenant General Sean MacFarland, who heads coalition forces in Iraq, is among a group of military leaders, administration officials and lawmakers who are fed up with "arbitrary" limits on troop numbers.

The last reinforcement of US troops in Iraq came in April, when Pentagon chief Ashton Carter announced the total number of troops would be augmented by 217, bringing the official tally up to 4,087.

The actual number, however, is higher because the Pentagon doesn't count certain categories of troops.

Obama has been reluctant to deploy additional forces to Iraq -- as well as to neighboring Syria -- to combat the IS group because he came to power on the promise of ending the war in Iraq and is wary of a gradual re-escalation.

Iraqi security forces have made significant gains against the IS group, and are in the process of clearing any remaining IS fighters from Fallujah.

Most US troops in Iraq serve in an advisory role with Iraqi partners, though some special operations forces have helped carry out anti-IS raids.

The American presence in Iraq is a sensitive one for the Iraqis too, especially among Shiite militias wary of US forces.