Deutsche Bank Is Crashing Again: Why One Hedge Fund Expects Much More Pain For European Banks, page-77

Also worth keeping in mind with $6T of foreign US Treasury holdings a price of $5000 to convert USD to gold would give the rest of the world the ability to completely drain the US of all its gold reserves...

US Gold reserves: 8133 tonnes = $1.3T (if gold is @ $5000)

...so not sure that would be such a wise move for the US. I get the feeling China and Japan would take that deal in a heartbeat.