But his confession and apology, in a nationally televised news conference, left other mysteries unsolved, like whether he had lied to his staff members about his whereabouts, whether the affair had definitively ended and whether he would resign from the governorship.

Sanford, 49, admitted that he had been in Buenos Aires for four days since last Thursday.

Sanford, a Republican who had been considered a possible presidential candidate in 2012, teared up as he spoke, taking more than seven minutes to apologise before getting to the crux of the matter.

“The bottom line is this,” he said. “I have been unfaithful to my wife.”

The Governor’s wife, Jenny, 46, issued a statement later in the day saying that while she loves her husband, she asked him to leave the family two weeks ago in a trial separation, though she still believes the marriage can be repaired.

The Governor said he would resign from his position as chairman of the Republican Governors Association. He will be succeeded by Gov Haley Barbour of Mississippi. A reporter tried to ask Sanford if he would resign from the governor’s office, but he did not answer.

Sanford’s acknowledgment was yet another blow to Republican hopes for a strong field of challengers to President Obama.

Sanford said his friendship with the woman began eight years ago and became a romance about a year ago. He said he had seen her three times since then.

Sanford implied he had ended the affair. “The one thing that you really find is that you absolutely want resolution,” he said. “And so oddly enough, I spent the last five days of my life crying in Argentina.”