DENVER -- The U.S. Department of Justice on Thursday sued a controversial and popular Arizona sheriff, alleging that his department was refusing to cooperate with an investigation into whether it discriminated against Latinos while trying to catch illegal immigrants.

The Justice Department said Maricopa County Sheriff Joe Arpaio was the first local law enforcement official in 30 years to refuse to provide documents in a federal civil rights probe. The federal government could withhold $113 million in funding from Maricopa County if Sheriff Arpaio cannot produce records demonstrating that he avoids racial discrimination.

"The actions of the sheriff's office are unprecedented. It is unfortunate that the department was forced to resort to litigation to gain access to public documents and facilities," said Assistant Attorney General Thomas E. Perez of the department's Civil Rights Division.

Sheriff Arpaio contended that the lawsuit was a political move by the Obama administration, which filed another high-profile suit against Arizona this summer to stop a tough new immigration law from taking effect.

"These actions make it abundantly clear that Arizona, including this sheriff, is Washington's new whipping boy," Sheriff Arpaio said in a statement. "Washington isn't playing fair, and it's time Americans everywhere wake up and see this administration for what it really is -- calculating, underhanded at times and certainly not looking out for the best interests of the legal citizens residing in this country."

Sheriff Arpaio, who calls himself "America's toughest sheriff," has drawn praise and criticism for his aggressive attempts to enforce immigration laws. Most prominent are operations dubbed "sweeps," in which his deputies fan out across immigrant neighborhoods, stopping people for sometimes-minor violations, such as jaywalking, and asking their immigration status.

Critics contend that the operations amount to racial profiling. Sheriff Arpaio says his deputies only look for people breaking the law, a contention he reiterated at a televised news conference Thursday in Phoenix. "I'm very confident that my deputies don't racially profile," he said.

The Obama administration last year revoked Sheriff Arpaio's authority to enforce federal immigration laws on the streets, which had little practical effect because the sheriff said state law lets him keep up his operations.

But his battle with the federal government predates President Barack Obama. In the summer of 2008, under then-President George W. Bush, the Justice Department launched a preliminary inquiry into allegations of racial profiling. In March 2009, the department expanded the inquiry into a full-fledged probe.

The investigation started with what federal officials contended was a routine document request -- 51 different categories of material. According to Thursday's suit, the department received just 11 pages. The last time the Justice Department had to sue to obtain documents in a civil rights probe was during a 1978 investigation of employment practices of a sheriff's department in Virginia.

For the past 18 months, Sheriff Arpaio has publicly said he would not let federal investigators into his jails or other facilities and dismissed the probe as politically motivated.

His lawyer met with Justice lawyers in Washington last week and contended that the material which the federal government requested was outside its scope of investigation.

This is not Sheriff Arpaio's first battle over documents related to possible civil rights abuses. His department faces a suit from an array of civil rights groups for allegedly racially profiling. A federal judge earlier this year found that his department improperly destroyed immigration-related paperwork that was evidence in that case, and he approved sanctions against the agency.

Sheriff Arpaio's stance has made him popular in Arizona, the main point of entry for migrants illegally crossing the Mexican border. He was one of the most prominent backers of SB 1070, the aggressive state law mandating that police verify the status of people they stop and also suspect are illegal immigrants.

A federal judge put the law's main parts on hold in late July in response to the Obama administration's suit, and the matter is expected to end up in the U.S. Supreme Court.Legal experts said that, despite the combustible backdrop of racial politics, a brash sheriff and local defiance of Washington, Thursday's lawsuit will turn on narrow legal matters, such as what the federal government can request under the 1964 Civil Rights Act.

Sheriff Arpaio's stance is "more your standard, hardball litigation than it is a challenge to the authority of the federal government," said University of Arizona law professor G. "Jack" Chin.

Both sides in the contentious immigration debate were quick to seize on Thursday's lawsuit.

"Unless a judge can put some serious sanctions [on him]), Arpaio will continue to thumb his nose at the entire justice system," said Lydia Guzman, president of the immigrant rights group Somos America, or We Are America, a plaintiff in the racial profiling case against the sheriff's office.

Arizona State Sen. Russell Pearce, appearing next to the sheriff at his news conference, said the Justice suit shows that federal civil rights investigators have not been able to turn up any evidence of misconduct by Sheriff Arpaio's department. "It's simply a witch hunt," he said.As he usually does when challenged, Sheriff Arpaio vowed to forge ahead with his operations. "I'm going to continue, maybe tomorrow, to enforce all the illegal immigration laws," he said. "I'm not going to be intimidated by the Justice Department."

Washington correspondent Daniel Malloy writes the "Pittsburgh On The Potomac" blog exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.