Acknowledging he has given inconsistent answers to Congress, President Barack Obama's pick to lead the Transportation Security Administration wrote to lawmakers to explain a reprimand he received for running background checks on his then-estranged wife's boyfriend two decades ago.

Erroll Southers, a former FBI agent whose nomination has been delayed by Republicans for unrelated concerns, sent a letter to senators in November to correct what he called a distortion of his record. As Democrats push for his speedy confirmation, the chairman of the Senate Homeland Security Committee said he maintained faith in the nominee.

"I am distressed by the inconsistencies between my recollection and the contemporaneous documents, but I assure you that the mistake was inadvertent, and that I have at all times taken full responsibility for what I know to have been a grave error in judgment," he wrote in a letter to Sens. Joe Lieberman, I-Conn., and Susan Collins, R-Maine.

"This incident was over 20 years ago, I was distraught and concerned about my young son, and never in my career since has there been any recurrence of this sort of conduct."

In an October affidavit for the Senate committee, he initially said he asked a San Diego police employee to run a background check on his then-estranged wife's boyfriend and was censured by his FBI superiors 20 years ago for what he said was an isolated instance.

But a day after the committee approved his nomination and sent it to the full Senate, he wrote to the senators and told them that he was incorrect, that he twice ran background checks himself.

In the letter correcting the record, Southers also said he downloaded law enforcement records and shared them. He said he forgot the incident in 1987 or 1988.

The letter was first reported by The Washington Post's Web site on Thursday. The letter, which was distributed to all members of the Homeland Security Committee and whose contents were verified to The Associated Press by a Democratic source, was dated Nov. 20.

Lieberman aide Leslie Phillips said the senator continues to support Southers.

"Twenty years ago, Mr. Southers committed a serious error in judgment," Phillips said. "He admitted that error and was disciplined for it. He went on to develop broad knowledge and build an excellent reputation in the areas of security and law enforcement. Mr. Southers was forthcoming about his past censure during his nomination process and about errors he made in recalling the details."

White House officials lined up behind Southers' nomination to head a Transportation Department agency that lacked a confirmed chief when a suspected terrorist failed to destroy a Detroit-bound airliner on Christmas Day.