The Pentagon is moving to increase the number of American troops in Iraq in the wake of new strikes that killed the Islamic State's finance minister and other top leaders of the terror group.
But senior US defence officials say the deaths will not "break the back" of the extremist group, which is in a fierce fight for an ancient city in Syria and has said it carried out the bombing at a football stadium in Iraq on Friday.
Defence secretary Ash Carter said the US progress in eliminating members of IS' "cabinet" was hampering its ability to conduct and inspire attacks against the West.
The announcement came as the battle to retake the Syrian city of Palmyra entered its third day and Iraqi forces continued their march to recapture Mosul. And the suicide bombing at the stadium south of Baghdad, which killed nearly 30 people, underscored the difficult fight ahead.
General Joseph Dunford, chairman of the Joint Chiefs of Staff, said recommendations on ways to increase US support for Iraq's ground fight against IS would be discussed with US president Barack Obama soon.
"The secretary and I both believe that there will be an increase in US forces in Iraq in coming weeks, but that decision hasn't been made," he said. He did not say how big that increase might be.
Gen. Dunford and Mr Carter said accelerating the campaign against IS would include more assistance like the artillery fire and targeting help that the US Marines provided earlier this week to Iraqi forces advancing on Mosul. But they said American forces remained well behind the front lines.
Using an acronym for the militant group, Mr Carter said the US was "systematically eliminating Isil's cabinet", killing several key members in strikes this week.
He would not provide details about the strikes, but a senior US official said the group's financial minister was killed along with two associates in a US raid in Syria.
Mr Carter said the finance minister, known by several names including Abdul-Rahman Mustafa al-Qaduli and Haji Imam, was a "well-known terrorist" who had a hand in plots outside Iraq and Syria.
He said al-Qaduli had been associated with IS 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 in Pakistan and was "responsible for some external affairs and plots".
Mr Carter said he was not aware of any link between al-Qaduli and this week's terrorist attacks in Brussels.
In a separate operation, a US air strike in Mosul killed another top IS leader, identified by Mr Carter as Abu Sarah. He said he was one of the leaders tasked with paying militant fighters in northern Iraq.
The successful attacks are part of a string of recent strikes targeting the leadership of the group, which has lost territory in both Iraq and Syria.
Earlier this month the Pentagon said it killed Omar al-Shishani, described as IS's "minister of war", in an air strike in Syria. In November, the Pentagon said an air strike in Libya killed Abu Nabil, another top IS leader.
Earlier this week military officials confirmed the creation of a US Marine outpost, dubbed Fire Base Bell, in Iraq.
Marines operating from the small base provided targeting assistance and artillery fire to support Iraqi troops retaking several villages in the initial stages of their march to Mosul. It's the first such base established by the US since it returned forces to Iraq in 2014.
Mr Carter has also said the US is looking at a number of options to "accelerate" the fight against IS. Those options have not yet officially been submitted to the White House for approval.
They could include sending additional US forces to Iraq, using Apache helicopters for combat missions, deploying more special operations forces or using American military advisers in Iraqi units closer to the front lines.