Treasury Secretary Janet Yellen, in a letter on Friday to congressional leaders, said the Treasury would begin using extraordinary measures Jan. 21.

Treasury secretary Janet Yellen, in one of her final major acts in office, warned Congress late Friday that the Treasury will need to begin "extraordinary measures" on Tuesday to avoid hitting the debt limit.

U.S. Treasury Secretary Janet Yellen said that the government will reach its statutory borrowing limit on Tuesday and begin employing "extraordinary measures" to keep from breaching the cap and risking a potential catastrophic default.