The White House rejected calls Monday from Ronald Reagan's (search) family and others to relax President Bush's restrictions on stem-cell research (search) in pursuit of potential cures for illnesses.

Bush signed an executive order in August 2001 that limited federal help to financing stem cell research on 78 embryonic stem cell lines then in existence. Because day-old embryos are destroyed when stem cells are extracted, the process is opposed by some conservatives who link it to abortion (search).

Shortly before Reagan's death, presumptive Democratic presidential nominee John Kerry and 57 other senators asked Bush to relax the restrictions. Nancy Reagan has long argued that using stem cells from embryos could lead to cures for a number of diseases like the Alzheimer's (search) that afflicted her husband. Bush opposes using embryos for stem cell research.

White House spokesman Scott McClellan said Bush continues to believe that his policy is the right one.

"The president came up with a policy that will allow us to explore the promise of stem-cell research, and do so in a way that doesn't cross a certain moral threshold that he set," McClellan said. "And I think he articulated his reasons for arriving at that decision. And that is his position, and that remains his position."

Moreover, he said, "we are still at a phase where we are conducting the basic research so that we can better understand the promise of stem-cell research. There's a lot we don't know at this point."

McClellan would not directly answer questions about whether Bush would be open to relaxing his policy if current "basic research" begins to show promise.

But, he said, "The president doesn't believe we should be creating life for the sole purpose of destroying life."