US governor admits 'wrong' affair
The Republican governor of the US state of South Carolina has admitted to an extra-marital affair.
Mark Sanford also said he would resign as chairman of the Republican Governors' Association.
He had earlier provoked controversy by disappearing on a visit to Argentina without informing anyone.
Mr Sanford, who had been a potential Republican candidate for the 2012 presidential elections, did not say whether he would be leaving his office.
In an emotional news conference, Mr Sanford said he had "let down a lot of people".
He said he had been having an affair for about a year with a "dear friend" he first met "very innocently" eight years ago.
"What I did was wrong. Period. End of story," he said.
He said his wife and family had known of the affair for the past five months and that he was resigning his post of chair of the RGA.
Mr Sanford went missing for several days earlier in the week.
I developed a relationship with... a dear, dear friend from Argentina and as a consequence I hurt her, I hurt you all, I hurt my wife, I hurt my boys, I hurt a lot of different folks
The search for the governor has fascinated Americans.
His staff had said he was walking on the Appalachian Trail in the east of the US, but his wife said she did not know where he had gone.
On Wednesday, he admitted he had been on a private visit to Argentina because he had "wanted to do something exotic".
The BBC's Justin Webb in Washington says Mr Sanford is known for enjoying spending time on his own.
But his decision to leave South Carolina without a leader for several days had left many questioning his judgement and may have cost him his future career, says our correspondent.
Mr Sanford has more than a year left in his second term as governor and is constitutionally barred from standing for office again, but has not said whether he will stand down.
The resignation is the latest problem to beset the Republican party.
Last week, Republican Senator John Ensign of Nevada admitted to an extra-marital affair with a member of his campaign staff.