A laboratory technician tests fluids at the Institute of Cellular Medicine, in San Jose in May 2010. (Juan Carlos Ulate/Reuters)

U.S. regulations expanding stem cell research have temporarily been blocked by a U.S. judge.

A non-profit group, Nightlight Christian Adoptions, contends that new guidelines on stem cells drafted by U.S. President Barack Obama's administration will reduce how many human embryos are available for adoption.

A U.S. district court issued a preliminary injunction Monday halting federal funding for human embryonic stem cell research.

The new guidelines, which allow researchers to use stem cells from surplus embryos donated by patients at fertility clinics, went into effect in July 2009.

They came out of the executive order issued by Obama in March 2009 in which he revoked restrictions on federal funding of stem cell research imposed by his predecessor, George W. Bush.

At issue in the lawsuit brought by Nightlight Christian Adoptions is whether the guidelines violate a law banning the use of federal funds to destroy human embryos.

Embryonic stem cell research "is clearly research in which an embryo is destroyed," Judge Royce Lamberth wrote in a 15-page ruling.

The Obama administration could appeal his decision or try to rewrite the guidelines to comply with U.S. law.

There was no immediate comment from the U.S. Department of Justice and U.S. National Institutes of Health, which funds medical research.

With files from The Associated Press