Treasury Secretary Steve Mnuchin said Sunday that permanent corporate tax cuts are necessary to spur economic growth before making individual tax cuts permanent.

Host Chris Wallace challenged Mnuchin, saying he doesn’t know what factors will be at play in 2025 or whether Congress would extend the tax cuts at that point.

“I don’t know that. Maybe I’ll be working for President Pence at the time, but I don’t know that," Mnuchin said on "Fox News Sunday." "We’ll know by then whether this creates growth or not. If it does, we’ll have an incredible economy… if it doesn’t, Congress will deal with it at the time."

A modified version of the Senate tax bill released last week shows that while a corporate tax cut would be permanent, individual tax cuts would expire in 2025.

The decision would help prevent the tax bill from adding to the deficit after 10 years, which is necessary in order to pass the legislation package with a simple-majority vote.

Democrats have frequently criticized the GOP tax reform proposals, calling them beneficial for the wealthiest Americans while doing little to assist the middle class.

Mnuchin said Sunday that permanently lowering the corporate tax rate from 35 percent to 20 percent is required “because we’re changing from an international system to a territorial system.”

Reforming the business tax code will help spur investment and growth, and create jobs domestically, Mnuchin argued. A stronger economy would then help pave the way for longer term tax cuts for the middle class, he said.

“Nobody thinks that’s going to be the case,” he said of the individual cuts expiring. “Of course Congress is going to vote down the road to keep these cuts.”

Mnuchin said he’s optimistic Congress will have a tax bill for President Trump to sign by Christmas.