WASHINGTON (Reuters) - Federal courts would be barred from striking the words "under God" from the Pledge of Allegiance to the American flag under a bill passed on Thursday by a House of Representatives split largely along party lines.

The Republicans in control of the chamber rejected Democratic claims that the measure was an unconstitutional bid to limit the power of the federal judiciary and an election-year ploy to rally social conservatives. It passed on a vote of 247-173.

Spurred by a celebrated but ultimately failed court challenge to the pledge in California, the bill is expected to die in the U.S. Senate without a vote as the U.S. Congress draws to an end this year. But that did not dampen Republican enthusiasm.

"We have heard a lot of legalese here ... (but) this is not very complicated," said Rep. Todd Akin, a Missouri Republican and the bill's chief sponsor.

"The simple question is whether school kids are going to be able to say the pledge the way we have done it for the past 50 years," Akin said.

Congress added the phrase "under God" to the pledge in 1954 as a symbolic way to distinguish the United States from the Soviet Union, its officially atheist Cold War foe.

Democrats argued that the House bill, the "Pledge Protection Act," would violate the Constitution's separation of powers between the government's judicial and legislative branches.

"I love the pledge," said House Minority Leader Nancy Pelosi, a California Democrat. But "this bill ... violates the spirit of pledge by professing a lack of faith in the constitutional framework."

The bill would essentially let only state courts hear constitutional challenges to the pledge in order to prevent what backers denounced as possible meddling by "activist" or "rogue" federal judges.

Earlier this year, the U.S. Supreme Court overturned a ruling by a federal appeals court in California that reciting "under God" in the pledge amounted to a violation of church-state separation.