In a rare move, North Carolina Republican Sen. Richard Burr announced Thursday that he will oppose the nomination of a U.S. attorney to his state until the investigation of John Edwards is complete.

Edwards, the two-time Democratic presidential candidate who last year admitted an affair with his former campaign videographer, Rielle Hunter, has been under federal investigation by prosecutor George Holding since at least the spring. On Nov. 30, President Obama announced his intent to nominate Thomas Walker to replace Holding, whose tenure expires in September 2010.

Walker's nomination has caused some consternation among the state's two senators, though both had recommended him for the job. The senators say they want Holding to be able to finish his probes into Edwards and former Gov. Mike Easley, before Walker takes the job.

North Carolina Democratic Sen. Kay Hagan had previously raised her concerns to the White House. But as recently as last week, a spokesman for Burr said the Republican senator was not planning to intervene.

Burr explained in a written statement Thursday that he opted to withhold his support because Walker had made political contributions to the officials under investigation. Burr did not mention the names of "those officials," but federal campaign finance records show Walker gave $750 to Edwards' presidential campaign in 2003. Walker also donated $1,250 to Barack Obama's presidential campaign.

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"Political contributions made by Mr. Walker to the former North Carolina elected officials currently under investigation represent a conflict of interest, and would potentially require his recusal from those very investigations," Burr said. "Given the importance of these investigations to the people of North Carolina, and in the interest of good governance and transparency, I believe the investigations must be directed by and have the full attention of the U.S. Attorney."

Burr said that he has told the White House that he will not return Walker's "blue slip" -- a form that home-state senators are asked to fill out regarding such nominees. Withholding the form can hold up a nomination though it is not an absolute veto.

Burr said that he will sign the slip after the investigation is complete, calling Walker "well-qualified" for the job when the time is right.

"Delaying this nomination will ensure that the investigations and potential prosecutions will proceed with impartiality, and in turn provide the public with full confidence that justice is served in an even-handed manner. At the same time, it will allow Mr. Walker to start his tenure as U.S. attorney free from any unfair specter of speculation and cynicism," Burr said.

It is not clear what Hagan will do. Spokeswoman Stephanie Allen said in a written statement Thursday that Hagan "maintains her position" and "believes George Holding should be allowed to finish his investigations of former public officials."

"She is continuing to impress this upon the administration, as she did in a conversation this week with the attorney general," Allen said.

Investigators are looking into whether Edwards misused campaign funds in the course of paying Hunter, who claims Edwards as the father of her child.

His political action committee paid Hunter $100,000 in 2006, and then a little more than $14,000 in 2007. Strangely, the same day Hunter was paid in 2007, a $14,000 sum listed for a "furniture purchase" was put into the account.

Edwards' admission of the affair came several months after he dropped out of the presidential race and endorsed Obama. Edwards denied wrongdoing in the federal investigation, putting out a statement in May saying he's "confident" no funds were used improperly.

Easley has been under investigation regarding his use of private aircraft for travel while in office and other issues.