David Plouffe, Obama's top political adviser, gave the warning to a dozen wealthy Democrats gathered at a Silicon Valley, Calif., office suite, The New York Times reported.
Obama needs help, Plouffe told the gathering, adding Democrats shouldn't believe all they read about all the money the president intends to raise for his re-election.
The Times said Obama's allies are telling supporters the huge cash advantage for Republicans could overwhelm Obama this fall.
Super PACs arose after a 2010 U.S. Supreme Court decision removing restrictions on corporate fundraising. Officially, they are independent-expenditure committees, but in reality they espouse candidates and can raise unlimited money from corporations and individuals.
The Times said early signs suggest Democratic super PACs are facing a hard road -- few have collected the six- and seven-figure checks the GOP super PACs are getting.
A super PAC supporting Obama, Priorities USA Action, is set to report $2 million in February donations. The Democratic super PAC and a related group raised about $6.1 million through 2011.
But that figure is dwarfed by the leading Republican super PAC, which took in $51 million last year and eventually hopes to raise $240 million, the Times said. The conservative oil men Koch brothers vow to raise another $200 million.