Treasury Secretary Jack Lew warned lawmakers on Monday that they will have to raise the debt limit by mid-October, sooner than previously expected.

In a letter to congressional leaders, Lew said his department will soon run out of the accounting maneuvers it’s been using to stave off default.

“Congress should act as soon as possible to protect America’s good credit by extending normal borrowing authority well before any risk of default becomes imminent,” Lew said in his letter.

The deadline, sooner than what some other forecasters had estimated, comes amid concern that Congress has no plan for handling the needed increase in what promises to be a contentious debate between Republicans and Democrats.