South Sudan opposition leader Riek Machar is still waiting for permission to travel to a peace retreat at the Vatican on Wednesday, according to a letter seen by The Associated Press.

The letter written Tuesday by Machar to the East African regional bloc, which must give him the permission to leave house arrest in neighboring Sudan, says his status had "not yet been determined" and requests 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 Pope Francis at the Vatican.

A regional bloc official declined to comment. Machar has been waiting to return to South Sudan next month to become a vice president under a power-sharing agreement.