Some medical researchers say they're let down U.S. President Barack Obama hasn't reversed Bush administration limits on human embryonic stem cell study.

Proponents expected Obama to lift Bush's 2001 restriction in his first week in office, when he issued executive orders to close the prison at Guantanamo Bay, Cuba, make government less secretive and fund international family planning groups that support abortion, they say.

"We were surprised and disappointed it wasn't in there," Coalition for the Advancement of Medical Research President Amy Comstock Rick told The Washington Post.

Her group is leading the Washington lobbying effort to lift the restriction.

"We're wondering why it's taking so long," she said.

President George Bush's restriction limited federal funding to studies of embryonic stem cell lines that were in existence Aug. 9, 2001, to keep tax dollars from encouraging embryo destruction.

The limitation was welcomed by people who said destroying human embryos is immoral but denounced by those who say it severely hinders research on hundreds of new cell lines developed since then, the Post said.

Such cells could lead to cures for a host of ailments because they can become any type of tissue in the body, proponents say.

Obama repeated his campaign promise to lift the restriction last week and senior Obama adviser David Axelrod told "Fox News Sunday" Obama was "considering" an executive order and would act soon.

The National Institutes of Health said it has started drafting guidelines to fund embryonic stem cell research.