"Early June is when we project that we will run out of cash, and there is a chance it could be as early as June 1. Of course, there is a lot of uncertainty," Yellen stated.
The US Treasury will keep the Congress updated on new developments, she added.
Earlier in May, the US Department of the Treasury said the US government will likely begin defaulting on its debt by June 1 if the congressional limit on the country's debt servicing is not raised by then.
In late April, House Republicans passed legislation to raise the debt ceiling in exchange for cuts in federal spending and other measures to reduce the deficit. However, Senate Democrats and US President Joe Biden rejected the proposal, saying it had no chance of becoming law. Inversely, House Speaker Kevin McCarthy said that a "no-strings-attached" debt limit increase would not pass the lower chamber.
Biden is scheduled to meet with McCarthy and other congressional leaders next week to negotiate the raising of the US debt limit.