The runoff had been scheduled for December 27, after an October 25 first-round vote marred by allegations of massive voter fraud.
The runoff was to pit Jovenel Moise -- backed by outgoing president Michel Martelly and the ruling party -- against Jude Celestin, the second-place vote-getter from more than 50 contenders in the first round of balloting.
The October presidential election was the latest attempt in the Americas' poorest country to shed chronic political instability and work toward development.
But reporting of the election results -- and now, the staging of the runoff vote -- has been plagued with delays and beset by protests alleging official corruption.
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Moise is a businessman and political novice who until now worked in agriculture, mainly growing bananas. His nickname during the campaign was "the banana man."
Celestin, making his second bid for the Haitian presidency, was disqualified from the second round in the 2010 election vote following a recount by the Organization of American States. This time, he had been considered the front-runner.
The first round of voting was relatively peaceful, in contrast to violence during August legislative elections that left two people dead.