The U.S.-led coalition against ISIS in Iraq pledges to send 1,500 more troops to Iraq, a top U.S. commander told BBC Monday.

This new pledge will be an addition to the already 3,100 US soldiers already promised to help out in Iraq to fight the militants, Lt Gen James Terry told BBC.

The troops will remain in an advisory role in Iraq and it is unclear how many extra troops the other coalition nations would provide

The coalition members reportedly discussed the issue and made the pledge at a security conference last week, Terry said.

At the conference, Terry said the airstrikes were ‘taking a toll’ on ISIS in Iraq and Syria. The US alone is responsible for the airstrikes as most of the coalition do not take part in them.

The Iraqi forces are becoming more “capable everyday”, Terry said.

The Combined Joint Task Force announced that coalition forces carried out 15 airstrikes in Syria and 31 in Iraq last week.

ISIS threatens to kill more hostages and is believed to impose its will on non-believers on its strict religion.

The pledge comes after the U.S. and NATO closed their combat command in Afghanistan, 13 years after invading the country to target Al Qaeda as a response to the Sept. 11 attacks.

Obama recently allowed American forces to launch operations against both Taliban and al Qaeda militants, broadening the mission of the U.S. forces that will remain in the country. They also will be permitted to provide combat and air support as necessary, while Afghan President Ashraf Ghani also considers resuming controversial night raids that could see Americans take part.

Up to 10,800 U.S. troops will remain in Afghanistan for the first three months of next year, 1,000 more than previously planned, said a NATO official who spoke on condition of anonymity to discuss troop deployments. As a result, there will be little, if any, net drop in U.S. troop numbers between now and Dec. 31, when the international combat mission formally ends.

By the end of 2015, however, American officials say the U.S. troop total will shrink to 5,500, and to near zero by the end of 2016.

The Associated Press contributed to this report

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