The US government plans to set up a "national bank" of embryonic stem cells for government-funded research, but still refuses to loosen restrictions on getting them from human embryos, according to a senior government official on Wednesday.

"The National Institutes of Health (NIH) will create a National Embryonic Stem cell Bank that will provide a ready source of human embryonic stem cells to scientists, ensure consistent quality of the lines and provide other technical support that will make it easier for scientists to use federally approved stem cells," Health and Human Services Secretary Tommy Thompson said in a letter to lawmakers.

"Before anyone can successfully argue that the stem cell policy should be broadened, we must first exhaust the potential" of currently available lines, he added.

The National Institutes of Health is also expected to establish three "centers of excellence" and use 18 million US dollars over four years in funding research on the currently available lines --which supporters of embryonic stem cell research say are not enough.

Embryonic stem cells, taken from days-old human embryos, can turn into any tissue in the body. Scientists hope to use them to grow replacement tissue to treat cancer, diabetes, spinal cord injuries and other diseases.

Many religious groups oppose the embryonic stem cell research as the culling of the stem cells will kill the human embryos.

President George W. Bush, who has ordered the NIH not to fund any research on human embryonic stem cells harvested after Aug. 9, 2001, has been accused of stifling groundbreaking research.

Earlier this month, 58 senators from both parties had asked the president to lift the restrictions.