Carter identified the senior IS leader as Haji Imam and described him as the group's finance minister. He said he was a "well-known terrorist'' who had a hand in terrorist plots outside of Iraq and Syria. He said he was not aware of any link between Haji Imam and this week's terrorist attack in Brussels.

"We are systematically eliminating ISIL's cabinet,'' Carter told a Pentagon news conference. "Indeed, the U.S. military killed several key ISIL terrorists this week, including we believe Haji Iman, who was an ISIL senior leader serving as a finance minister and who also was responsible for some external affairs and plots.''

Asked about the impact of these killings, Carter said, "Leaders can be replaced. However, these leaders have been around for a long time. They are senior, they are experienced.''

Carter said he would not reveal whether the IS finance leader was killed in Syria or Iraq or whether the mission was an airstrike or a ground raid.

Appearing at the news conference with Carter, Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, said recommendations on ways to increase U.S. support for Iraq's ground fight against IS are going to be discussed with President Barack Obama soon.

"The secretary and I both believe that there will be an increase in U.S. forces in Iraq in coming weeks, but that decision hasn't been made,'' Dunford said. He did not say how big that increase might be.

The U.S. military has killed numerous Islamic State leaders in recent months. Earlier this month the Pentagon said it killed Omar al-Shishani, described as the Islamic State's "minister of war,'' in an airstrike in Syria. In November, the Pentagon said an airstrike in Libya killed Abu Nabil, another top IS leader.

Carter said Haji Imam has been associated with the Islamic State dating back to its earliest iteration as al-Qaida in Iraq. He said he had worked under Abu Musab al-Zarqawi as a liaison for operations with Pakistan.

"The removal of this ISIL leader will hamper the organization's ability to conduct operations both inside and outside Iraq and Syria,'' Carter said.

(AP)