Article I, Section 8 of the U.S. Constitution grants Congress the power to coin money and regulate the value thereof.
On the October 16, 2011 episode of The Progressive Radio News Hour with Stephen Lendman, Ellen Brown, author of Web of Debt, relayed what a former director of the Bureau of Engraving and Printing said in the 1980s (at 13:18):
“The government could solve its debt problem by just minting some large coins. That there’s no limit on how many coins they can make, and there’s no limit on the face value of the coin. So today, for example, you could stamp out 15 $1 trillion coins and you’d take care of the debt and you’d have a little money left over. And, a number of economists actually picked up on that, and there’s this whole dicussion out there now about how you could solve the problem with some $1 trillion coins which you would then put in the government’s bank account, basically. So you don’t actually ever spend the coins, but you can draw against them, and it’s a way to create money…“
And I wholeheartedly agree with both the constitutionality and simplicity of the proposal.