The chairman of the Electoral Council, Pierre-Louis Opont, said there had been security concerns.
Opposition candidate Jude Celestin has vowed to boycott the vote.
There have allegations of voting fraud in November's first round elections, and street protests calling for the runoff to be postponed have turned violent at times.
The current Haitian President, Michel Martelly, is constitutionally barred from seeking re-election.
Ruling party candidate Jovenel Moise, a banana exporter, won the largest share of the vote in November's first round elections, with 33%, but fell short of a majority.
He has little political experience but has the backing of Mr Martelly.
He is due to face ex-state construction company head Jude Celestin, who came second with 25%.  It is the second time Mr Celestin has stood for the presidency.
Mr Celestin has said he will boycott the runoff because of the fraud claims.
He said he would not participate unless electoral reforms were carried out, although he is yet to formally withdraw.
Opposition parties and local observers have also said the election's first round in November was marred by fraud.
President Martelly's term ends in less than three weeks and correspondents say if there is no election it could push Haiti over the edge into more political instability.
Whoever takes over from Mr Martelly will face the daunting task of reconstructing the country - which was devastated by an earthquake in 2010 and has been forced since to rely largely on international donations and foreign aid.
Haiti's electoral authorities have postponed a presidential runoff election for a third time.