The Bipartisan Policy Center (BPC), a centrist think tank that closely tracks the debt limit, said the Treasury Department will likely run out of ways to keep the U.S. solvent sometime after the start of the fiscal year. BPC originally projected the so-called x-date to occur as soon as the beginning of October, but slightly delayed and narrowed that window after an unexpectedly strong summer surge in federal revenues.

BPC experts warned that a potential slowdown and deepening uncertainty driven by rising COVID-19 cases could shift that window sooner, bringing the U.S. closer to an unprecedented default on the national debt.

“It’s unclear what the next month or two is going to bring in federal revenues, and that can make a big difference in terms of the timing,” said Shai Akabas, director of economic policy for BPC.