Washington  - South Carolina's governor admitted Wednesday to an affair with an Argentinian woman, ending a bizarre mystery that began with his sudden disappearance from his home state last week.

Mark Sanford, a Republican, vanished on June 18 without telling either his family or staff where he was headed.

In a press conference after his return Wednesday morning, Sanford said he went to Buenos Aires to visit an Argentinian woman with whom he'd had an affair for about a year.

"The bottom line is this: I've been unfaithful to my wife," Sanford said with tears in his eyes. "I hurt you all. I hurt my wife, I hurt my boys."

Sanford, once considered a potential presidential candidate, said he would resign as head of the Republican Party's governors' association. But he gave no clues as to whether he would resign as governor of South Carolina.

Sanford's disappearance had attracted national media attention and sharp criticism from politicians of both parties in the state, who believed he had left South Carolina vulnerable should there be an emergency.

Sanford said he had known the Argentinian woman, who was not named, for about eight years, but the affair began one year ago. They met three times during the year and exchanged a series of romantic emails. His wife Jenna had known for about five months.

Jenna Sanford said that she, too, had not known her husband's whereabouts over the past week. In a statement, she explained that she had asked her husband to leave the home two weeks ago.

"Because of this separation, I did not know where he was in the past week," said Jenna. Neither she nor the couple's four children were at Sanford's side during Wednesday's press conference.

"I deeply regret the recent actions of my husband Mark and their potential damage to our children," she said, but added that the two might still work through it. "I believe Mark has earned a chance to resurrect our marriage."

Sanford is the second high-level Republican in a week to disclose an affair. Senator John Ensign of Nevada admitted to an affair last week and resigned as the fourth-ranking Republican in the Senate.

Sanford's staff was apparently kept in the dark about the affair and mystery trip to Buenos Aires. On Tuesday, a statement from his office said he was spending the week hiking the Appalachian Trail, which runs along the East Coast of the United States.

The governor acknowledged he may have misled his staff, telling reporters it was "my fault in shrouding this larger trip."

South Carolina's The State newspaper caught Sanford returning Wednesday morning at the airport in Atlanta, Georgia. At the time he told the paper he travelled to Buenos Aires to get "a break" after a hectic legislative session.

"I wanted to do something exotic ... It's a great city," Sanford told the newspaper. "I don't know how this thing got blown out of proportion."

The newspaper also published some of the emails between Sanford and the woman, identified only as Maria, dating back to July 2008. (dpa)