The letter written by Machar to the East African regional bloc, which must give him permission to leave house arrest in neighboring Sudan, said his status had "not yet been determined" and he requested approval to go.
The retreat, also to be attended by South Sudan's president, is meant to foster peace after a five-year civil war. It comes a month after President Salva Kiir met with Pope Francis at the Vatican. Brazille Musumba, spokesman for the regional bloc, would not comment directly on Machar's letter. "I can only state that we support every effort to bring lasting peace to South Sudan," Musumba told AP.
Machar has been waiting to return to South Sudan next month to become a vice president under a power-sharing agreement.