(CNN) - Sen. Mike Crapo, R-Idaho, will not contest the charge that he was driving under the influence early last Sunday at his January court appearance, his spokesman said.
Spokesman Lindsay Nothern acknowledged that the results of a blood alcohol test conducted at a detention center differed from those at the time of his roadside arrest, but he was not certain why the levels differed.
Results of the detention center breathalyzer test were not immediately available.
Police in the Washington suburb of Alexandria said Crapo was arrested on suspicion of DUI early last Sunday after running a red light. The initial test showed his blood alcohol level was .110.
"Sen. Crapo was identified as the driver and arrested after failing several field sobriety tests," police spokesman Jody Donaldson said in a statement last week. "He was taken into custody without incident and transported to the Alexandria Adult Detention Center where he was released on a $1,000 unsecured bond."
Virginia law stipulates a $250 fine and license suspension for one year for a blood alcohol level of .080 to .140, with increased penalties for higher levels or repeat offenses.
Crapo has not spoken about the circumstances surrounding the incident but said in a statement from his office last week: "I am deeply sorry for the actions that resulted in this circumstance. I made a mistake for which I apologize to my family, my Idaho constituents and any others who have put their trust in me.
"I accept total responsibility and will deal with whatever penalty comes my way in this matter. I will also undertake measures to ensure that this circumstance is never repeated."
Crapo is set to appear in court on January 4, the day after he and other legislators are sworn in as members of the 113th Congress.
He has represented Idaho in the Senate since 1999. Before that, he was in the U.S. House of Representatives for six years. He was re-elected in 2010 with 71% of the vote. He's a member of the Senate's "Gang of 8."
Crapo is a member of the Church of Jesus Christ of Latter-day Saints, which prohibits the use of alcohol among its members.
- CNN's Gregory Wallace and Kevin Liptak contributed to this report