WASHINGTON (AP) - A California physician and lawyer whose legal fight against the words "under God" in the pledge of allegiance has drawn national attention now says he will join a lawsuit seeking the removal of all references to God and religion from President-elect Barack Obama's inauguration ceremony.

Michael Newdow believes references to God or religion are unconstitutional. He wants to remove the phrase "so help me God" from the oath of office and block the invocation prayer from Pastor Rick Warren.

The suit was filed Tuesday in D.C. District Court. The plaintiffs include 17 other people and atheist and humanist organizations. He sued to remove religion from inaugurations in 2001 and 2005 but lost both cases.

Newdow is an ordained minister of the Universal Life Church and founder of FACTS (First Amendment Church of True Science), an organization that advocates strong separation of church and state.