By Terry Baynes

Oct 15 (Reuters) - The U.S. Supreme Court agreed on Monday to consider whether Arizona can demand that voters show proof of U.S. citizenship to register to vote in federal elections.

The high court will not hear the case before the Nov. 6 U.S. election, ensuring that the disputed registration requirement in Arizona will not be in effect.

The legal dispute over the registration requirement dates back to 2004 when Arizona voters passed a ballot initiative, Proposition 200, designed to stop illegal immigrants from voting. The measure amended state election laws to require voters to show proof of citizenship to register to vote, as well as identification to cast a ballot at the polls.

Arizona residents, Indian tribes and civil rights groups sued to challenge measure.

The registration law requires voters to present "satisfactory evidence" of U.S. citizenship, including a driver's license number, naturalization papers, U.S. birth certificate or passport.

It is one of many measures nationwide championed by Republicans and put in place at the state level that Democrats say are intended to make it more difficult for certain voters who tend to vote Democratic to cast ballots.

Arizona, which borders Mexico, has been a focal point of immigration laws. In a landmark case, the U.S. Supreme Court in June upheld Arizona's provision on immigration status checks by police. But it also struck down rules in the state's measure that would, among other things, ban illegal immigrants from soliciting work in public places.

While the 9th U.S. Circuit Court of Appeals upheld Arizona's right to require voter identification at polling places, the court in April found that the citizenship requirement conflicted with a 1993 federal law designed to make it easier for people to register to vote in federal elections by using a federal registration form.

'OPERATE HARMONIOUSLY'

The state requirement and the federal scheme did not "operate harmoniously," the appeals court found, so the federal rules won out.

On appeal, Arizona argued that the 9th Circuit owed more deference to the state's authority to administer federal elections.

The dispute over the citizenship registration requirement differs from challenges to state voter ID laws unfolding in courts across the country. The Arizona case focuses on the tension between federal and state authority over elections while the voter ID challenges focus on the laws' alleged discriminatory effects.

Voter ID laws in U.S. states have suffered a series of setbacks in courts ahead of the November election. The laws require voters to show certain types of identification before voting.

In 2008, the U.S. Supreme Court upheld a voter identification law passed by Indiana, leading many experts to conclude that it would be hard to challenge such laws in court.

Since the last presidential election in 2008, some 15 states have passed or tightened legislation requiring people to identify themselves before voting.

Defenders of the laws, mostly Republicans, say the laws are needed to prevent people from fraudulently impersonating registered voters at the election booth. Opponents, mostly Democrats, complain that obtaining identification documents is an undue burden that could disenfranchise the poor, minorities and the elderly - people who may tend to vote Democratic.

The June ruling in the Arizona immigration case went to the heart of a fierce national debate between Democrats and Republicans over the 11.5 million illegal immigrants the U.S. government estimates to be in the country.

President Barack Obama has vowed to push for comprehensive immigration legislation if re-elected. Opinion polls show Hispanic voters overwhelmingly support Obama.

Republicans generally back stricter controls on illegal immigration than Democrats. In the Republican primaries to pick a presidential nominee, Mitt Romney, Obama's challenger, took a hard line, saying he supported what he called self-deportation for illegal immigrants.

In Monday's order, the Supreme Court granted Arizona's appeal without comment. A decision is expected by the end of June 2013.

The case is Arizona v. The Inter Tribal Council of Arizona Inc et al, U.S. Supreme Court, No. 12-71.

For Arizona: Arizona Solicitor General David Cole.

For The Inter Tribal Council of Arizona: Jon Greenbaum of the Lawyers' Committee for Civil Rights Under Law.

For Jesus Gonzalez et al: Nina Perales of the Mexican American Legal Defense and Education Fund.

For the Coconino County plaintiffs: Jean Wilcox of the Office of Coconino County Attorney.