PORT-AU-PRINCE (Reuters) - Haiti on Thursday heeded foreign pressure and amended the results of its November first-round elections, setting up a presidential run-off excluding a government-backed candidate hit by fraud allegations. The countrys Provisional Electoral Council (CEP) said former first lady Mirlande Manigat and musician Michel Sweet Mickey Martelly were the two top finishers of the chaotic November 28 vote, ahead of government technocrat Jude Celestin. The two leaders would contest a run-off set for March 20 to replace outgoing President Rene Preval. Prevals mandate formally ends on Monday, but he has parliament approval to stay on if necessary until May 14 so he can hand over to an elected successor. These definitive CEP results, which reversed a preliminary count that had placed Celestin second and in the run-off, averted a showdown between Haitis government and electoral officials and the Organisation of American States and Western donors including the United States. They were in line with a revision carried out by OAS experts, who, addressing allegations of widespread fraud and irregularities in the first-round vote tallies, had recommended Martelly go through to the run-off instead of Celestin, Opposition matriarch Manigat, 70, did not gain enough votes to win outright in the first round. No percentages, just the positions, were immediately announced on Thursday. After Martelly supporters rioted in December against these initial results, the United Nations, United States and other western donor governments had piled pressure on Haitis leaders and electoral authorities to adopt the OAS recommendation. There were fears the unrest could escalate and derail the elections, threatening the handover of power by Preval and putting at risk billions of dollars of aid pledged to help the poor Caribbean nation recover from a devastating 2010 earthquake. The results announcement came as a relief to some. Im very happy about this decision. I was very anxious because I didnt know what was going to happen if Martelly did not get into the run-off. Now I can open my business without fear, said Jonel Joseph, 42, who has an auto parts business. The top UN official in Haiti, Edmond Mulet, and OAS Secretary General Jose Miguel Insulza welcomed the first-round results. We hope the results are received by everyone in an environment of trust and tranquillity, Insulza said. But there were those who saw US meddling. What a disgrace to the United States government: the richest country in the world has forced one of the poorest to change the results of its presidential election, literally under the threat of starvation . ... This attempt to impose an illegitimate government on Haiti will backfire, said Mark Weisbrot, co-director of the Washington-based Centre for Economic Policy and Research. The Western Hemispheres poorest state, which lost more than 300,000 people in the earthquake, is also grappling with a deadly cholera epidemic hampering reconstruction efforts. Adding to the already nervous political atmosphere is the possible return of ousted former President Jean-Bertrand Aristide, who has asked the government for a diplomatic passport so he can come home from exile in South Africa. Washington and other Western donors are wary that Aristides return could inflame Haitis volatile politics. The firebrand leftist ex-Roman Catholic priest retains a passionate following in Haiti. He became Haitis first freely elected president in 1990 before being ousted by an armed revolt in 2004. Haitis uncertain outlook has been further clouded by the reappearance of ghosts from its turbulent past. Former dictator Jean-Claude Baby Doc Duvalier came home from exile in January, running into corruption and human rights charges, and Aristide is now preparing his own homecoming. Despite a visit on Sunday by Secretary of State Hillary Clinton to emphasise US backing for the OAS results option, the Provisional Electoral Council had kept Haitians and its foreign partners guessing over whether it would follow it. Celestin, a protege of Preval, had refused to drop out despite pressure from his own INITE party. Ordinary Haitians were sanguine about whether the first-round results could bring stability. We take what they give us. Now I hope life can continue and we can live in peace, said Jonaldo St Jules, 20.