The Supreme Court appeared closely divided Wednesday about an Arizona tax-break program that provides millions of dollars in scholarships for students at private religious schools.

The conservative justices indicated they are likely to rule against a challenge to the Arizona program that says it amounts to an unconstitutional state endorsement of religion. The court's liberals suggested they have problems with the state's tax credit.

Justice Anthony Kennedy, often the decisive vote in ideologically divided cases, asked questions of both sides that did not tip his hand.

The Obama administration joined with the state in arguing in strong defense of the program, saying the Arizona residents who oppose it should not even be allowed to bring their lawsuit in federal court.

For the past 13 years, Arizona has allowed residents to send up to $500 to a tuition scholarship organization that they would have otherwise paid the state in taxes on their incomes.

The problem, in the view of the American Civil Liberties Union-backed challenge to the program, is that most of the money goes to groups that award scholarships on the basis of religion and require children to enroll in religious schools.