South Carolina Gov. Mark Sanford waves to the media as he leaves the family home on Sullivan's Island, S.C., on Thursday. The family is staying there after Sanford admitted to having an affair with a woman from Argentina. (Mary Ann Chastain/Associated Press)

South Carolina Gov. Mark Sanford apologized to senior state officials Friday for keeping them in the dark when he travelled to Argentina last week to visit his mistress.

Sanford, who confessed to the affair and secret trip during a news conference Wednesday, told his state agency chiefs he put them in awkward positions by lying about his location.

The Republican governor had told staff he was hiking the Appalachian Trail.

During his regular weekly meeting with the agency chiefs, Sanford likened his confession and future to that of the biblical King David. Sanford said King David fell mightily but picked up the pieces and built from there.

Sanford disappeared to Buenos Aires last week, returning Wednesday to reveal the affair and publicly apologize to his wife and four sons, his supporters and constituents. He also resigned as chairman of the Republican governors.

Wife found letter

His wife on Friday told The Associated Press she found out about the affair in January after discovering a letter from his mistress, a woman who has been identified in the media as "Maria."

Jenny Sanford said she told him to end the affair and was shocked this week when she found out he'd gone to Argentina to see the woman. She says she believed her husband had gone somewhere to work on writing a book.

She said she stayed with her husband until their four sons finished the school year before taking them to the family's coastal home on Sullivan's Island, S.C.

Earlier Friday, the man who could replace Sanford said he's not calling for the governor's resignation.

Lt.-Gov. Andre Bauer, a fellow Republican, told The Associated Press Friday that he spoke to Sanford on Thursday and "could tell he had done a lot of soul-searching."

"Mark Sanford is still my governor and regardless of what his decision is, I'm going to stand by and try to help him," Bauer told the news agency.

Bauer and Sanford have not been political allies and there's speculation Bauer will run for the governor's job when Sanford's term expires next year.

Will repay money: governor

In a statement issued Thursday, Sanford said he would pay back roughly $13,700 in taxpayer money used to pay for a 2008 trip to Argentina and Brazil because he used the trip to meet with the woman.

It includes close to $10,000 for his plane ticket, $500 for lodging and $2,100 for an aide's plane ticket.

"I made a mistake while I was there in meeting with the woman who I was unfaithful with," the governor said in a statement.

Sanford, who has been a possible GOP presidential candidate for 2012, said he told his wife about the affair five months ago.

He said he had known the woman for about eight years and had been romantically involved with her for about a year, seeing her three times since the affair began.

With files from The Associated Press