WASHINGTON—Treasury Secretary Janet Yellen said the U.S. will hit its borrowing limit in the middle of next month, triggering the use of “extraordinary measures” to keep the federal government from defaulting on its obligations.

Treasury Secretary Janet Yellen suggested in a letter to Congress on Friday that the department doesn’t think the U.S. will need to take “extraordinary measures” on Jan. 2 to avoid defaulting on its obligations,

Treasury Secretary Janet Yellen warned Congress that the country could hit the debt ceiling as soon as Jan. 14 in a letter sent Friday.

The notification to Congress is the clearest sign yet that the fight to avoid default will likely take place in the early months of the new Trump administration.