The nation's largest group of atheists and agnostics filed a lawsuit Tuesday seeking to block an architect from engraving "In God We Trust" and the Pledge of Allegiance at the Capitol Visitor Center in Washington.

The Madison-based Freedom From Religion Foundation's lawsuit, filed in U.S. District Court in western Wisconsin, claims the taxpayer-funded engravings would be an unconstitutional endorsement of religion.

The House and Senate passed identical resolutions this month directing the Architect of the Capitol to engrave "In God We Trust" and the pledge in prominent places at the entrance for 3 million tourists who visit the Capitol each year.

The resolution came in response to critics who complained Congress spent $621 million on the new three-story underground center without paying respect to the nation's religious heritage. The center opened in December after years of construction.

The foundation is seeking a court order to stop the engravings, which the Congressional Budget Office estimates will cost less than $100,000.

"In God We Trust" has been the national motto since 1956 and has appeared on U.S. currency since 1957.

The lawsuit says both the motto and the words "under God" in the pledge were adopted during the Cold War as anti-communism measures. Engraving them at the entrance to the U.S. Capitol would discriminate against those who do not practice religion and unfairly promote a Judeo-Christian perspective, it says.

Members of Congress who supported the measure swiftly denounced the lawsuit.

"This lawsuit is another attempt by liberal activists to rewrite history and deny that America's Judeo-Christian heritage is an essential foundation stone of our great nation," said Rep. Steve King, R-Iowa.

Rep. Daniel Lungren, R-Calif., said he was expecting a lawsuit but called the claims "patently absurd."

The foundation also is challenging the constitutionality of the National Day of Prayer in federal court.