"I remain firmly opposed to changing the president's policy," he said, but "should this bill pass, I think the president would veto it."

The bill stipulates that embryos can be used for federally funded stem cell research regardless of the date of their creation, but it requires that only embryos originally created for fertility treatment could be used. It also asks for the beneficiaries of the treatment to provide written consent for embryo donation.

While federal funding has been limited, some states have hiked their support for stem cell research significantly with hopes to attract eminent scientists and private investment. Last fall, California authorized as much as $3 billion over the next decade to fund research efforts.

Lawmakers sponsoring the bill lauded state initiatives but said a strong federal stem cell research program was needed to ensure nationwide scientific cooperation and strict standards to conduct the research. Co-sponsors include Sens. Arlen Specter, R-Pa., and Tom Harkin, D-Iowa, and Rep. Diana DeGette, D-Colo.