By Marius Bosch and Ed Stoddard
JOHANNESBURG (Reuters) - Haiti's exiled former President Jean-Bertrand Aristide said on Thursday he will be returning home before Sunday's presidential run-off election, despite opposition from the United States.
The United States has urged Aristide -- in exile in South Africa since he was ousted in 2004 -- to delay his return until after the March 20 poll. The left-wing populist's party was barred from the ballot.
Aristide told a news conference in Johannesburg that he was flying out of South African on Thursday night.
"The great day has arrived. The day to say goodbye before returning home," Aristide said late on Thursday, adding that he and his family "must leave today."
The election has been overshadowed by Aristide's expected return.
The vote is being closely watched by the United States and other Western donors which have invested heavily in trying to steer the fragile Caribbean state to lasting stability, and bankrolling its recovery from a crippling 2010 earthquake.
But Aristide said he was wanted back in Haiti.
"In Haiti they are also very happy because they were waiting for us and they have wanted for us to be back home as soon as possible," Aristide said.
Washington has been piling pressure on Pretoria to delay Aristide's departure. President Barack Obama has called his South African counterpart, Jacob Zuma, to impress upon him the importance of Aristide not returning before the poll.
"The United States, along with others in the international community, has deep concerns that President Aristide's return to Haiti in the closing days of the election could be destabilizing," National Security Council spokesman Tommy Vietor said.
Aristide will fly out of South Africa on a chartered aircraft which is expected to arrive in Port-au-Prince by noon on Friday, his lawyer Ira Kurzban said.
Collins Chabane, a minister in the presidency, told reporters on Thursday South Africa could not prevent Aristide from returning to Haiti and the matter was being dealt with through diplomatic channels.
"We are not sending former President Aristide to Haiti. He was given the passport by the government of Haiti and you can't hold him hostage if he wants to go," Chabane said. Aristide has long accused the United States of helping engineer his ouster, and his supporters accuse Washington of playing an active role in keeping him in South Africa.
Election officials have barred his party from running a candidate in the election, which was tainted by allegations of widespread fraud during November's first round of voting.
Aristide became Haiti's first freely elected president in 1991 but was overthrown after seven months. Re-elected in 2000, his second term was soured by economic instability and violence.
(Additional reporting by Wendell Roelf in Cape Town and Jane Sutton in Miami; Editing by Elizabeth Fullerton)