The president can, in principle, invoke the 14th Amendment to the US Constitution, which states that “the validity of the public debt of the United States, authorized by law, …shall not be called in question.”
Some analysts believe Biden may argue that he has a constitutional duty to avoid default and thus exceed the debt limit to continue spending already approved by Congress.
However, the move would almost certainly lead to a prolonged legal wrangle, which could destabilize financial markets.
Republicans have warned that Biden cannot act unilaterally and that the solution has to come through Congress.
This week, a union of public sector employees sued Treasury Secretary Janet Yellen and Biden, arguing that they are constitutionally bound to defy the debt limit.
The lawsuit is trying to ensure that workers are not penalized while loan payments are given priority in the event of a default.