The White House acknowledged Wednesday that President Obama would consider putting U.S. troops in "forward-deployed positions" to advise Iraqi forces in the fight against the Islamic State -- even while insisting U.S. troops would not be sent back into a "combat role" in Iraq. 

Obama and his top advisers appeared to be threading a needle as they carefully clarified how exactly U.S. troops might be used, a day after Joint Chiefs Chairman Gen. Martin Dempsey opened the door to approving "U.S. military ground forces." 

The White House continued to insist Wednesday that a "combat role" has in fact been ruled out, and that U.S. troops will not be engaging the Islamic State on the ground. 

Speaking at MacDill Air Force Base in Tampa, after visiting U.S. Central Command, Obama told troops: "I will not commit you and the rest of our Armed Forces to fighting another ground war in Iraq." 

He vowed that the U.S. forces currently deployed to Iraq to advise Iraqi forces "will not have a combat mission." Instead, he said, they will continue to support Iraqi forces on the ground, through a combination of U.S. air power, training assistance and other means. 

But the White House is no longer ruling out deploying ground troops in some capacity short of a "combat" mission. Shortly after Obama spoke, White House Press Secretary Josh Earnest clarified that Dempsey was talking about the possible need to put U.S. troops already in Iraq into "forward-deployed positions with Iraqi troops." 

Earnest said that step has not yet been necessary, but if Dempsey asks to "forward deploy" American advisers, "the president said he would consider it on a case-by-case basis." 

He said, in that scenario, U.S. troops "would be providing tactical advice to Iraqi security forces" or be in position to call in airstrikes. 

Vice President Biden also kept the door open to ground troops being put to some purpose in Iraq. After a speech in Des Moines, the vice president was asked during a stop at a local diner whether he agreed with Dempsey's assessment about using ground troops if needed. 

"His conclusion is it is not needed now. We'll determine that ... based on how the effort goes," Biden said. 

Earnest still stressed that any such troops "would not have a combat role" and "would not be personally or directly engaging the enemy." 

The comments mark the latest evolution of the administration's stance on how the U.S. military could be deployed, though aides insist this is not a slippery slope. 

Speaking at a Senate hearing on Wednesday, Secretary of State John Kerry underscored the message that "U.S. ground troops will not be sent into combat in this conflict." 

Despite these pledges, Dempsey on Tuesday appeared to challenge the administration position when, during testimony before a Senate committee, he said he might recommend U.S. ground troops if Obama's current strategy doesn't work. 

"My view at this point is that this coalition is the appropriate way forward," Dempsey said. "I believe that will prove true, but if it fails to be true and if there are threats to the United States, then I of course would go back to the president and make a recommendation that may include the use of U.S. military ground forces." 

Dempsey provided one example of a scenario where he might recommend U.S. ground forces, saying they could be used to help Kurdish and Iraqi forces retake Mosul, now controlled by the Islamic State, or ISIS, by accompanying them or providing close-combat advice. 

The remarks caused controversy in Washington as well as Baghdad. 

Iraq's new prime minister dismissed the notion that the struggle could lead to U.S. forces again fighting on the ground in his country. 

"Not only is it not necessary, we don't want them. We won't allow them," Prime Minister Haider al-Abadi said in an interview with The Associated Press. 

Top House Democrat Nancy Pelosi also said Democrats "are not supporting combat troops." 

While Obama faces pressure from his left flank not to open the door to ground troops, he also faces pressure from more hawkish officials to keep that option open. 

Former Defense Secretary Robert Gates told CBS News that "there will be boots on the ground if there's to be any hope of success in the strategy." 

The Associated Press contributed to this report.