Treasury Secretary Steve Mnuchin got a lesson in civics on Sunday when Fox News host Chris Wallace was forced to explain why President Donald Trump cannot single out certain parts of bills to veto if he doesn't like them.

During an interview on Fox News Sunday, Mnuchin complained that Democrats had negotiated for an increase in non-defense spending as a part of the omnibus budget bill.

"That's going to happen next time," Wallace pointed out. "When the next spending bill comes up in October, they're going to be demanding parity as well. I'm not saying it's right or wrong, but it is reality."

"It doesn't need to be reality," Mnuchin opined. "I think they should give the president a line-item veto."

"That was ruled unconstitutional by the Supreme Court," Wallace noted.

"Well again, Congress could pass a rule, okay, that allows them to do it," Mnuchin replied.

"No, no," Wallace interrupted. "It would have to be a constitutional amendment."

Mnuchin accused Wallace of trying to "get into a debate."

"There's different ways of doing this," he charged, quickly changing the subject. "My comment is, it's clear what happened. The Democrats, in order to get us military spending, demanded a massive increase in non-military spending. And the president made the decision this time that that was worth it because military spending, given what's going on in Iran, in North Korea, in Venezuela, in Russia -- all around the world where we're using sanctions. We need to make sure we have a military that has the necessary resources."