The case sets up an emotional showdown over God in the public schools and in public life. It will settle whether the phrase "one nation under God" will remain a part of the patriotic oath as it is recited in most classrooms.
"It's really a no-brainer that the justices would take this case," said CBS News legal analyst Andrew Cohen. "It has national significance."
The court will hear the case sometime next year. Most legal experts think the high court will overturn the lower court ruling and uphold the pledge as is.
"This is a fairly clear sign, I think, that the justices are likely to overrule the lower court ruling," Cohen said. "I don't think the court would have taken the case merely to affirm what their colleagues in California had ruled."
Ruling on a lawsuit brought by Sacramento atheist Michael Newdow, a 9th U.S. Circuit Court of Appeals panel decided in June 2002 by a 2-1 margin that Newdow's daughter should not be subjected to the words "under God" at her public school.
The court said the phrase was an endorsement of God, and the Constitution forbids public schools or other governmental entities from endorsing religion.
That ruling, if allowed to stand, would strip the reference from the version of the pledge recited by about 9.6 million schoolchildren in California and other western states.
A national uproar followed the ruling. President Bush and Congress immediately condemned the decision, which would prevent public schoolchildren from reciting the pledge in the nine western states covered by the nation's largest — and, critics charge, most liberal — appeals court.
Those states are Alaska, Arizona, California, Hawaii, Idaho, Montana, Nevada, Oregon and Washington. The effect of the ruling still is on hold.
The full appeals court in February rejected the Bush administration's request to reconsider its decision. That set up the move to the Supreme Court.
Cohen notes that the words "under God" weren't part of the original pledge: They were added in 1954. Supporters of the new wording said it would set the United States apart from godless communism.
The justices could eliminate the words by saying they were added for religious purposes, Cohen reports. Or they could determine that "under God" is akin to the words "In God We trust" on money, which are considered constitutional because they consist of what the law calls "ceremonial deism."
The First Amendment guarantees that government will not "establish" religion, wording that has come to mean a general ban on overt government sponsorship of religion in public schools and elsewhere.
The Supreme Court has already said that schoolchildren cannot be required to recite the oath that begins, "I pledge allegiance to the flag of the United States of America."
The court has also repeatedly barred school-sponsored prayer from classrooms, playing fields and school ceremonies.
The 9th U.S. Circuit Court of Appeals said the language of the First Amendment and the Supreme Court's precedents make clear that tax-supported schools cannot lend their imprimatur to a declaration of fealty to "one nation under God."
The administration, the girl's school and Newdow all asked the Supreme Court to get involved in the case.
The court, however, agreed only to hear the appeal from the school district. The administration will be able to weigh in separately. The court also said it will consider whether Newdow had the proper legal footing to bring the case.
In its legal filings so far, the administration has argued that the reference to God in the pledge is more about ceremony and history than about religion.
The reference is an "official acknowledgment of our nation's religious heritage," similar to the "In God We Trust" stamped on coins and bills, Solicitor general Theodore Olson told the court. It is far-fetched to say such references post a real danger of imposing state-sponsored religion, Olson wrote.
Moreover, being a parent of a child in public school does not give a parent the power to dictate what the child will be exposed to, Olson said.
"Public schools routinely instruct students about evolution, war and other matters with which some parent may disagree on religious, political or moral grounds," he said in his appeal.
The administration also claimed that Newdow cannot sue on behalf of his daughter because he does not have custody of her. Newdow and the child's mother, Sandra Banning, have waged a long and bitter custody battle over the child, who lives with her mother. Newdow claims a judge recently gave him joint custody of the girl, whose name is not part of the legal papers filed with the Supreme Court.
To complicate matters, Banning has told the court she has no objection to the pledge.
Newdow holds medical and legal degrees, and says he is an ordained minister. He is representing himself in filings at the high court, and has said he will argue his case in person.
"Those who deny the existence of a supreme being have been turned into second class citizens by a government that continuously sends messages that 'real Americans' believe in God," Newdow told the justices in his appeal.
Newdow sued the school, Congress, President Bush and others to eliminate the words "under God." He asked for no damages.