WASHINGTON -- The Pentagon said Friday it was moving to increase the number of American forces in Iraq and announced that U.S. forces have killed the finance minister for the Islamic State of Iraq and Syria, or ISIS. "We are systematically eliminating ISIL's cabinet," Defense Secretary Ash Carter said, using a different acronym for the group.

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 ISIS are going to be discussed with President 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 told Pentagon reporters during a briefing. He did not say how big that increase might be.

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The group's financial minister was known by several names: Abdul-Rahman Mustafa Mohammed, Haji Iman, Haji Imam and Abu Iman, Haji Ayman and Abu Alaa al-Afari.

CBS News national security correspondent David Martin reports that the U.S. offered a $7 million bounty for the senior ISIS official, which among ISIS fighters is second only to the $10 million bounty for the group's leader.

U.S. Secretary of Defense Ash Carter, left, and Chairman of the Joint Chiefs of Staff Gen. Joseph Dunford speak to press about counter-ISIS operations at the Pentagon March 25, 2016. Department of Defense/Navy Petty Officer 1st Class Tim D. Godbee/Handout via Reuters

The successful attack is part of a string of strikes targeting the group's leadership even as it losses territory in both Iraq and Syria. Dunford said there has been "indisputable" momentum against ISIS in recent weeks, as coalition airstrikes and Iraqi ground forces target the group's leaders, command and control structure and financing.

"By no means would I say that we are about to break the back of ISIL or that the fight is over," Dunford said, but added that there are a lot of reasons to be optimistic.

Carter said the senior ISIS leader killed 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 him and this week's terrorist attacks in Brussels.

Carter said he has been associated with ISIS dating back to its earliest iteration as al Qaeda in Iraq. He said he had worked under Abu Musab al-Zarqawi as a liaison for operations in 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 at a Pentagon news conference.

He added: "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."

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