Obama 'Would Order' US Troops Into Combat If ISIS Got Nuclear Weapon

— -- President Obama has been unwavering and definitive in declaring he will not deploy U.S. ground troops into combat to fight ISIS militants. Period.

But for the first time since the start of then anti-ISIS offensive dubbed Operation Inherent Resolve, the president volunteered a scenario which he said would change his mind.

“If we discovered that [ISIS] had gotten possession of a nuclear weapon, and we had to run an operation to get it out of their hands, then, yes,” the president told reporters at a news conference in Brisbane, Australia, on Sunday. “I would order it.”

There is no indication that ISIS currently possesses or could easily obtain a nuclear weapon, officials say.

Still, Obama’s declaration of a nuclear weapon in the hands of ISIS is a noteworthy new “red line” – and a very high bar for a U.S. offensive role on the ground.

White House Confirms Death of American Aid Worker Peter Kassig in New Video

3 Times Obama Administration Was Warned About ISIS Threat

Jimmy Carter Faults Obama on ISIS

Gen. Martin Dempsey, chairman of the joint chiefs and Obama’s top military adviser, has consistently kept the door open to deployment of U.S. ground troops in combat situations ever since anti-ISIS military operations began, but has yet to formally recommend it.

Last week, Dempsey testified on Capitol Hill that the Pentagon is “certainly considering” whether to embed U.S. military advisers with Iraqi combat units deployed to the front lines. Obama has also maintained openness to the idea, but already rejected one recommendation to do so.

“Yes, there are circumstances in which [Dempsey] could envision the deployment of U.S. troops. That’s true everywhere, by the way,” Obama said Sunday. “That’s his job, is to think about various contingencies. And, yes, there are always circumstances in which the United States might need to deploy U.S. ground troops.”

ABC News’ Luis Martinez contributed to this report