"Our government has forced what I believe is a false choice between sound science and moral values," Obama said as he signed documents changing U.S. science policy and removing what some researchers have said were shackles on their work.
"It is about ensuring that scientific data is never distorted or concealed to serve a political agenda -- and that we make scientific decisions based on facts, not ideology," Obama said.
Researchers said the new president's message was clear: Science again matters in American life.
Opponents saw it differently: a defeat for morality in the most basic questions of life and death.
"The action by the president today will, in effect, allow scientists to create their own guidelines without proper moral restraints," Family Research Council president Tony Perkins said.
The most immediate effect will allow federally funded researchers to use hundreds of new embryonic stem-cell lines for promising but still long-range research in hopes of creating better treatments, possibly even cures, for conditions ranging from diabetes to paralysis.
Until now, those researchers had to limit themselves to 21 stem-cell lines created before August 2001, when former president George W. Bush limited funding because of "fundamental questions about the beginnings of life and the ends of science."
But experts warn not to expect stem-cell cures or treatments anytime soon.
One company this summer will begin the world's first study of a treatment using human embryonic stem cells in people who recently suffered spinal cord injuries.
Research institutions on Monday were gearing up to ask for more freely flowing federal money, and the National Institutes of Health was creating guidelines on how to hand it out and include ethical constraints.
It will be months before the stem-cell money flows; the average NIH stem-cell grant is $1.5 million spread out over four years.