Yellen: US could default on debt as soon as June 1

Debt ceiling watchers have had June 15 circled on their calendars for weeks now as an important date. The crucial question: Will the government have enough in the bank to stay afloat until then?

A new letter from Treasury Secretary Janet Yellen says that her guess is that the answer is no.

"Our best estimate," she said in the letter, "is that we will be unable to continue to satisfy all of the government’s obligations by early June, and potentially as early as June 1, if Congress does not raise or suspend the debt limit before that time."

The letter, released on Monday afternoon and addressed to House Speaker Kevin McCarthy, is likely to reignite fears in the financial world that an immediate default - and the economic turmoil that it likely to follow - could be just weeks away.

This was Yellen's first update on the closely-watched question since January when she projected the X-date could be exhausted by early June.

Mid-June is an important period for the debt ceiling talks because it's the next time Treasury's coffers will see a sizable influx of money. Taxpayers will be providing the second installment of their estimated taxes for 2023 around that time.

In her letter, Yellen acknowledged that government could still reach that June 15 date, adding that it is possible "the actual date that Treasury exhausts extraordinary measures could be a number of weeks later than these estimates."

As of April 27, the Treasury Department’s general account had a closing balance of about $296.2 billion. The balance sheet may improve for a few more days as final April tax returns are processed before beginning a gradual decline.

Experts fear that the balance reaching zero - and the default that would follow - could set off steep declines in markets and likely cause an immediate recession with further economic repercussions being felt around the world.

Other experts see a 'peak danger zone' in July

Monday's letter from Yellen offers a more aggressive estimate than those recently produced by a series of outside analysts who downplay the chances of a June default.

One of those updated projections came from Wrightson ICAP, a close observer of the billions that flow in and out of the Treasury department every day. The research group is now most focused at this point on late July as the "peak danger zone" for default, according to a new outlook released Monday. Wrightson ICAP still projects a 10-20% chance of default ahead of that June 15 date.

Wrightson ICAP's “confidence interval around our June forecasts tightens a little with each passing day, as the scope for surprises narrow,” chief economist Lou Crandall tells Yahoo Finance.