Washington(CNN) Treasury Secretary Steven Mnuchin asserted Sunday Congress could give President Donald Trump "line-item veto" power -- something the Supreme Court has ruled unconstitutional. Fox News host Chris Wallace was forced to explain to him that Congress could not overrule the Supreme Court without amending the Constitution.

"Democrats demanded a massive increase in non-military spending," Mnuchin told Chris Wallace in an interview on Fox News Sunday. Mnuchin suggested that line-item veto power would give the President the ability to thwart Democratic demands in future spending bills.

The Supreme Court ruled the line-item veto unconstitutional in 1998, saying it gave the President the power to unilaterally change or repeal parts of legislation passed by Congress.

"It doesn't need to be reality, and I'm not going to comment on what the President will do, but as you heard him say, he's not planning on doing this again. I think they should give the President a line-item veto," Mnuchin said Sunday.

Wallace responded by noting that line-item veto power has "been ruled unconstitutional by the Supreme Court."

Mnuchin responded: "Congress could pass a rule, OK, that allows them to do it."

Wallace, in turn, explained that would require a constitutional amendment, to which Mnuchin said: "There's different ways of doing this."

Trump had urged lawmakers to grant him line-item veto power when he signed a $1.3 trillion spending bill that Congress sent to him just hours earlier.

"To prevent the omnibus situation from ever happening again, I'm calling on Congress to give me a line-item veto for all government spending bills," he said, expressing unhappiness with the massive bill and the haste with which it was passed. Trump added that he agreed to sign the bill to deliver a boost in defense spending.