Joel Sawyer, right, grabs South Carolina Gov. Mark Sanford's arm as he continues to answer questions after he admitted having an affair. (Mary Ann Chastain/Associated Press)

South Carolina Gov. Mark Sanford, who couldn't be found earlier this week, admitted Wednesday he had flown to Argentina to meet a woman with whom he had been having a year-long affair.

"I've been unfaithful to my wife," an emotional Sanford said at a news conference Wednesday. "I developed a relationship with what started as a dear, dear friend from Argentina."

Sanford, 49, said he had spent the last five days "crying in Argentina" but the affair is now over.

The governor, considered by some to be a rising star in the Republican party and a possible presidential candidate for 2012, apologized to his wife, Jenny, and his four sons.

Sanford said he revealed the affair to his wife five months ago.

He would not say whether he would resign as governor but said he will step down as head of the Republican Governors Association.

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.

"What I did was wrong. Period," he said.

Staff gave wrong information

The governor had not been seen in public since June 18, and reporters began asking questions about his whereabouts.

His staff had said he had gone hiking on the Appalachian Trail, something Sanford acknowledged he had told his aides he might be doing. He admitted he never corrected that impression after he left for South America.

"I let them down by creating a fiction with regard to where I was going," Sanford said. "I said that was the original possibility. Again, this is my fault in ... shrouding this larger trip."

When news first broke about his mysterious disappearance, Jenny Sanford told The Associated Press she did not know where her husband had gone for the Father's Day weekend.

His family did not attend the news conference, but his wife issued a statement saying she asked the governor to leave two weeks ago and not contact the family.

The governor said he wants to reconcile with his wife, and Jenny Sanford's statement said her husband has earned a chance to resurrect their marriage.

"This trial separation was agreed to with the goal of ultimately strengthening our marriage," she said.

Sanford's announcement came a day after another prominent Republican, Senator John Ensign of Nevada, apologized to his GOP Senate colleagues after revealing last week that he had an affair with a campaign staffer and was resigning as head of the Republican Policy Committee.

With files from The Associated Press