Roh Geon-ho could be interviewed Sunday, The Korea Times reported. He was in the United States but agreed to return to Seoul.
Park Yeon-cha, who is under indictment for bribery, has told investigators that Roh, president at the time, asked him for $1 million in 2007, the Yonhap News Agency reported. Park allegedly exchanged South Korean won for dollars, packed the cash in a suitcase and gave it to Jung Sang-moon, one of the president's aides.
On his Web site, Roh said his wife got money from Park in payment of a debt.
Park, a shoe manufacturer, was one of the former president's major campaign contributors.