ATLANTA - Georgia Attorney General Thurbert Baker is once again refusing Gov. Sonny Perdue's request to sue the federal government, this time over the state's voting check system.

In a letter to Secretary of State Brian Kemp on Thursday, Baker said he won't sue the Obama administration to implement Georgia's system of checking the citizenship of newly registering voters.

"Litigation against the United States is not a minor matter to be engaged lightly, especially when the costs of such litigation will be substantial," Baker wrote. He estimated a lawsuit could cost more than $250,000 and the state should continue to work with the Justice Department to get the measures cleared.

Baker blamed Kemp and his predecessor, fellow Republican Karen Handel, for failing to get the Justice Department all the information it needs to act on the matter.

The Justice Department has repeatedly rejected Georgia's voting check systems and Kemp has accused the department of playing politics.

Thursday's letter marks the second time that Baker has defied Perdue's order to sue.

Last month, the Democratic attorney general, who is seeking his party's nomination for governor, said he would not challenge a new federal health reform law saying the state lacked a viable legal claim. Perdue has named an outside counsel to sue on behalf of Georgia.

Perdue spokesman Bert Brantley said Thursday that would likely happen again in this case.

Brantley said the Justice Department "seems interested in delay, delay, delay and then refusal."

"We feel like we have not been getting a fair hearing ... it's been a frustrating process."

But Baker said he has met personally with head of the Justice Department's civil rights division and believes the department "is sincere in its desire to assist the state of Georgia" in getting the voter verification system cleared. The state is also looking to implement a new law that would require newly registering voters to provide proof of their citizenship.

Under the federal Voting Rights Act of 1965, Georgia and other states with a history of discriminatory voting practices must preclear any changes to election rules with the Justice Department or through the federal courts.

Implemented in 2007, Georgia's voter verification system had checked new voters against information in databases held by the Georgia Department of Driver Services or Social Security Administration.

After a challenge was filed by voting rights groups in the weeks leading up to the 2008 elections, a federal three-judge panel said the state must seek Justice Department preclearance under the Voting Rights Act.

The Justice Department's Civil Rights Division rejected the checks in May and October of last year saying they disproportionately impact minority voters.

Kemp on Thursday said Baker "has again refused to represent Georgia voters in federal court, choosing instead to play politics with the integrity of our elections."