US-based lawyer Ira Kurzban told French news agency Afp that Aristide had yet to finalise his trip back to Haiti.
"President Aristide is still here in South Africa,” he said. “We are trying to work out the logistics for him to be able to leave as soon as possible, and hopefully before Sunday.”
The United States had urged Aristide not to return to Haiti before Sunday's presidential election. They fear the homecoming of the three-time former leader could reopen old tensions ahead of the vote.
South Africa has publically said that it has no control over Aristide's departure, but Kurzban said the 57-year-old was waiting for the government there to complete arrangements for his return to Haiti.
"This is a decision by the South African government, working with the Haitian government, to make sure all the logistics are done, security is arranged and so forth. Our hope is it will be done quickly.
"It may be on a commercial flight or it may be on a private plane. We have not been told as to what those details are yet. Hopefully we're going to find out very soon.
"We're just waiting to find out whether it's going to be today, tomorrow, the next day. But our hope is that it will be before Sunday."
Kurzban told Afp on Wednesday that Aristide feared a new Haitian government may try to block his return if he waited until after the election.
Sunday’s vote will see 70-year-old Mirlande Manigat, a former first lady and academic, face off against popular singer Michel Martelly, 50.
November’s first round was marred by violence and the country is still struggling to recover from an earthquake that hit in January last year, killing some 250,000 people.