Carter, and Ahtisaari, the former president of Finland, may also be joined by former Irish President Mary Robinson and former Norwegian Prime Minister Gro Harlem Brundtland in North Korea April 26-28, a diplomatic source told South Korea's Yonhap news agency.
North Korea has invited Carter to visit Pyongyang with a goal of mending relations between the two Koreas, Yonhap reported.
Carter will visit Seoul April 29 to brief officials on the result of his Pyongyang trip. The U.S. State Department said Carter's trip is "strictly private."
"Carter's coming visit will provide a chance to see if there is a change in North Korea's behavior and also gauge the possibility of a breakthrough in the deadlock over the talks," an unnamed state department official said.
Carter recently said he would "try to induce the North Koreans to give up their nuclear weapons … what we want is a peace treaty."
Carter visited North Korea last year to bring back an American man who was held for illegally entering the country. He did not meet with North Korean leader Kim Jong-il on that trip.