SULLIVANS ISLAND, S.C. -- South Carolina first lady Jenny Sanford said she warned her husband not to see his mistress before a trip last week and was shocked he met her in Argentina anyway.

Jenny Sanford told The Associated Press on Friday that she discovered Gov. Mark Sanford's affair in January when she found a letter from him to the other woman.

The governor was told to end his affair, Jenny Sanford said. She said that he agreed to.

When the governor told her recently he needed time alone to write, she specifically warned him not to visit the mistress, Jenny Sanford said. She said that she was shocked to learn this week that he'd gone to Argentina to do just that.

Jenny Sanford said she stayed with her husband while their four sons finished the school year in Columbia before leaving him for their coastal home on Sullivans Island.

On Wednesday, the Republican governor admitted to an affair with a friend he met eight years ago from Argentina.