A would-be bank robber allegedly demanded “20,000 in large bills” from a Manhattan teller Wednesday afternoon before being busted by cops for the botched heist, police sources said.

The suspect, identified by sources as Jared Mitchell, walked into the TD Bank on Eighth Avenue near the Port Authority bus terminal at about 3 p.m.

Mitchell allegedly passed the teller a note that read, “I WANT $20,000 IN LARGE BILLS,” the sources said.

The teller hit the silent alarm and Mitchell ran off, but was arrested by nearby cops, law enforcement sources said.

The suspect was arrested a week prior for another attempted robbery at a Chase Bank in Times Square, sources said.