"Five trillion in new tax cuts? That is like trying to put out a prairie fire with gasoline," the president told a crowd at the Iowa State Fairgrounds Thursday night, the Des Moines Register reported.
Though Iowa has only six electoral votes, it is among a dozen states viewed as critical for the president to win in November and he spent Thursday campaigning there.
"You know this journey started in Iowa," Obama told a campaign rally. "And that's why we're going to be spending a lot of time in Iowa this time round."
Obama has visited Iowa nines times as president.
He said the tax cut his all-but-certain GOP rival Romney wants would only compound the nation's debt.
The president labeled a speech Romney delivered in Des Moines 10 days ago "more like a cowpie of distortion."
A Romney spokesman said Obama "has no standing when it comes to fiscal responsibility" because he failed to keep his campaign promise to cut the deficit in half by the end of his first term.