More U.S. doctors are refusing to treat patients for religious reasons, causing a collision between religious freedom and discrimination laws.

The list of services that some doctors are refusing to perform includes artificial insemination, use of fetal tissues and prescribing Viagra, USA Today said Friday.

Jill Morrison of the National Women's Law Center said problems occur when physicians offer procedures to some patients but not others.

USA Today said the California Supreme Court is scheduled to hear a lawsuit over a fertility treatment denied to a lesbian. A gay man in Washington state recently settled out of court with a doctor who refused to prescribe him Viagra.

Patrick Gillen, legal counsel for a Michigan-based public interest law firm that defends religious freedom, told the newspaper doctors shouldn't be required to perform procedures that violate their religious faith, especially "if the patients can get the treatment elsewhere."

Copyright 2007 by United Press International