Washington ? A federal judge on Monday temporarily blocked government rules expanding stem cell research, a blow to the Obama administration that could stall potentially lifesaving research.

The nonprofit group Nightlight Christian Adoptions contends that the government’s new guidelines will decrease the number of human embryos available for adoption and implantation. Nightlight helps individuals adopt human embryos that are being stored in fertilization clinics. The group provides domestic, international and embryo adoption services to families in all 50 states.

A federal appeals court had ruled that two fellow plaintiffs, doctors who do research with adult stem cells, were entitled to sue over the new guidelines, prompting U.S. District Judge Royce Lamberth on Monday to reverse a decision he made in October when he dismissed the lawsuit.