SAN FRANCISCO, Calif. (AP) -- An atheist who has spent four years trying to ban the Pledge of Allegiance from being recited in public schools is now challenging the motto printed on U.S. currency because it refers to God. Michael Newdow seeks to remove "In God We Trust" from U.S. coins and dollar bills, claiming in a federal lawsuit filed Thursday that the motto is an unconstitutional endorsement of religion. Newdow, a Sacramento doctor and lawyer, used a similar argument when he challenged the Pledge of Allegiance in public schools because it contains the words "under God." He took his pledge fight to the U.S. Supreme Court, which in 2004 said he lacked standing to bring the case because he did not have custody of the daughter he sued on behalf of. An identical lawsuit later brought by Newdow on behalf of parents with children in three Sacramento-area school districts is pending with the 9th Circuit Court of Appeals, after a Sacramento federal judge sided with Newdow in September. The judge stayed enforcement of the decision pending appeal, which is expected to reach the Supreme Court. Congress first authorized a reference to God on a two-cent piece in 1864. The action followed a request by the director of the U.S. Mint, who wrote there should be a "distinct and unequivocal national recognition of the divine sovereignty" on the nation's coins. In 1955, the year after Congress inserted the words "under God" in the Pledge of Allegiance, Congress required all currency to carry the motto "In God We Trust." "The placement of 'In God We Trust' on the coins and currency was clearly done for religious purposes and to have religious effects," Newdow wrote in the 162-page lawsuit he filed against Congress. Newdow's latest lawsuit came five days after the U.S. Supreme Court rejected, without comment, a challenge to an inscription of "In God We Trust" on a North Carolina county government building. In doing so, the justices upheld the Richmond, Va.-based 4th U.S. Circuit Court of Appeals, which ruled that "In God We Trust" appears on the nation's coins and is a national motto. "In this situation, the reasonable observer must be deemed aware of the patriotic uses, both historical and present, of the phrase 'In God We Trust,'" the appeals panel ruled in upholding the inscription's display.