During an interview for Politico published this week, US Treasury Secretary Steven Mnuchin had a strong message for Congress. In short, Mnuchin implied, failure to pass tax cuts means the stock market will blow up.

“There is no question that the rally in the stock market has baked into it reasonably high expectations of us getting tax cuts and tax reform done,” Mnuchin said in the interview.

“To the extent we get the tax deal done, the stock market will go up higher. But there’s no question in my mind that if we don’t get it done you’re going to see a reversal of a significant amount of these gains.”

Mnuchin also gave his “absolute guarantee” that Trump will sign tax legislation by year’s end, despite Trump’s own uncertainty expressed on Monday.

“I would like to see it be done this year,” Trump told reporters on Monday. “But don’t forget it took years for the Reagan administration to get taxes done — I’ve been here for nine months. We could have a long way to go, but that’s OK.”