Warren Buffett-

Warren Buffett said Wednesday the threat to not raise the nation's debt limit "after you've already spent the money" is a "political weapon of mass destruction" comparable to poison gas and shouldn't be used by either party.

"I know it's been used in the past, but we used the atomic bomb back in 1945 but we decided we weren't going to do something like that again," he said hours before the government's midnight deadline to raise the debt limit or possibly default.

Buffett called on both sides to pledge not to use the debt limit as a weapon. "There are plenty of weapons that can be used," like filibusters, he said.

In a live interview on CNBC's "Squawk Box, the Berkshire Hathaway chairman said he doesn't expect the U.S. will do anything to damage its 237-year reputation of paying its bills on time, but if it does it would be a "pure act of idiocy" and "asinine."

"Credit worthiness is like virginity, it can be preserved but not restored very easily, so it is crazy to play around with it," he said.