"I have been considering the 14th Amendment," Biden told reporters Tuesday after a meeting with top congressional leaders from both parties failed to produce a breakthrough in the debt-ceiling standoff.

Biden added: "The problem is it would have to be litigated. And in the meantime, without an extension, it would still end up in the same place."

Why is the 14th Amendment under discussion?

Some constitutional experts argue the debt ceiling - which sets a cap on the amount the U.S. can borrow - violates the 14th Amendment, which says in Section 4 the "validity of the public debt of the United States, authorized by law, including debts incurred for payment of pensions and bounties for services in suppressing insurrection or rebellion, shall not be questioned."

Rather than seeking congressional approval to raise the debt limit, according to the theory, the Biden administration could challenge the legality of the debt limit by having the Treasury continue to issue new debt to fulfill its financial obligations.

Biden pointed to the opinion of Laurence Tribe, professor emeritus at Harvard Law School and constitutional law scholar, who came around to the 14th Amendment theory after dismissing it in 2011 when President Barack Obama faced the risk of default.

Tribe, in a New York Times op-ed Sunday, wrote "the question isn't" whether the president has the authority to "tear up" the federal debt limit statute. "The right question is whether Congress − after passing the spending bills that created these debts in the first place − can invoke an arbitrary dollar limit to force the president and his administration to do its bidding." Tribe argues the answer is no.