In testimony before the Senate Armed Services Committee Tuesday, Gen. Lloyd Austin, commander of U.S. Central Command, pointed to the need for "additional capability" to retake the ISIS stronghold of Mosul in Iraq, as well as Raqqa, Syria, the de facto capital of ISIS's self-declared caliphate.
"Clearly there are things that we will want to do to increase the capability a bit, to be able to increase the pace of operations, and that will require some additional capability," Austin said.
"We have gone through and done some analysis ... to see what types of things we need to provide," he continued. "And we have made those recommendations."
While Austin declined to share the recommendations in the hearing, he said additional U.S. military personnel could help develop better intelligence on the ground, potential provide more advise-and-assist teams and help with some logistics.
"We could increase some elements of the Special Operations footprint," he explained.
Whether to field additional troops is likely something Austin's expected successor, Gen. Joseph Votel, commander of U.S. Special Operations Command, will have to confront when he takes over leadership of Central Command.
Votel, who testified in his current capacity alongside Austin, is scheduled to have his nomination hearing for the CENTCOM position before the same committee Wednesday.
In his testimony, Votel said that ISIS poses the greatest immediate threat because of its immediate abilities and desires to attack beyond its base in Iraq and Syria.
But he warned that Iran may pose a greater threat to U.S. interests in the region in the long term.
When pressed on the current status of the effort to retake Raqqa, Votel said there is a "strategy" in place to eventually take the city from ISIS. But perhaps in a nod to the various ethnic realities in a region with Arab and Kurdish forces, Votel said there is currently no plan in place on how to hold Raqqa.
In Syria, Austin said he has asked for "permission" to restart a program to train and equip indigenous forces to go after ISIS "using a different approach" from the previous program that ended in failure after graduating only a handful of troops.
The new program would focus on a smaller set of people to train who would then "enable" larger groups allied with the U.S. and its allies inside Syria to learn from that training once the forces re-enter the battlefield.
Gen. David Rodriguez, commander of U.S. Africa Command, who also testified Tuesday, said the growing threat posed by ISIS inside Libya requires the United States and its international allies to "do more," calling the North African country a failed state.
While the United States continues to push for a political settlement in Libya that would allow the formation of a functioning government, the United States has also recently launched airstrikes against ISIS leaders and facilities as the group's presence continues to grow.
And as the United States continues its efforts to train and equip the security forces in Afghanistan, Austin said a "review" of the current plan to reduce the level of U.S. forces in Afghanistan by the end of the year is in order based on the changing nature of the situation there since the battle plan was drawn up.
"When the situation changes so that those facts are no longer valid or the assumptions that you made are no longer appropriate, then I think you have to go back and revisit your plan," he said.