Several nations have pledged to send a total of about 1,500 troops to support the U.S.-led military campaign against
Army Lt. Gen. James L. Terry said Monday that the expected new force, nearly half the size of the 3,100-member American contingent, will be deployed to help train, advise and assist Iraqi and Kurdish troops battling the Sunni extremists.
"We'll pick up more and more capability as we bring more coalition members into our staff," Terry told reporters in his first interview since he was given the command in October.
Terry would not say which countries or how many have agreed to send troops because, he said, details have not been finalized. The pledges were made during meetings last week, he said.
U.S. officials say 40 nations are involved in the effort to push back Islamic State. U.S. warplanes and drones have carried out more than 1,000 airstrikes since August, and Britain, France, Canada, Saudi Arabia, Jordan, the United Arab Emirates, Bahrain and Qatar have flown dozens of additional missions.
Iranian jets also recently conducted several airstrikes in Iraq, but Tehran is not part of the U.S.-led coalition.
The U.S. and its allies conducted 31 airstrikes in Iraq and 15 in Syria in the last three days.
Although the growing air campaign has slowed the militants from pushing closer to Baghdad or the Kurdish capital, Irbil, Iraqi forces have yet to recapture any of the major cities or towns seized by the militants.
Because bombing in urban areas would cause civilian casualties, U.S. warplanes have attacked militants only on roads or in the open. Uprooting them from cities and towns will require Iraqi ground forces, U.S. officials say.
Thousands of Iraqi soldiers fled, or saw their units collapse in combat, after Islamic State fighters first swept across the border from Syria in the spring and summer, and the new government in Baghdad is struggling to rebuild a credible force.
The Pentagon plan calls for training up to 5,000 Sunni tribal fighters in Anbar province, a mostly Sunni enclave west of Baghdad where Islamic State has besieged the Haditha dam complex and reportedly carried out massacres of Sunni tribe members who refused to join the militants.
The Shiite Muslim-dominated Iraqi army is unpopular in Anbar, however, and may not fight hard to retake Sunni territory or to win support from Sunni residents, who see the troops as an occupying army. U.S. officials say an American-trained Sunni force might be more effective.
The Pentagon also plans to resume training Shiite security forces that can retake Shiite areas, including Mosul, Iraq's second-largest city.
Defense Secretary Chuck Hagel, who is on a farewell visit to several U.S. outposts before he leaves office, visited a U.S. Army installation in northern Kuwait that provides weapons and equipment for military operations in the region.
On Monday, Hagel thanked several hundred troops, saying their work was "absolutely critical" for operations against Islamic State. Iraqi forces have been encouraged as a result of the U.S. effort, he told them.