"I regret to say it is unfortunate that the elections will be postponed," commission head Hanna Nasser told reporters.
"It has become clear to us that conducting elections in the Gaza Strip is not likely to happen," he said.
Palestinian president Mahmud Abbas had called for presidential and parliamentary elections to be held on January 24, when the four-year mandate of the current Hamas-dominated parliament runs out.
But Hamas, which has controlled Gaza since June 2007, blasted the president`s decree as unconstitutional because his own mandate ran out in January.
Abbas has said that he would not stand for re-election because of what aides said was his frustration with the inability by the US to get Israel to freeze settlements in order to resume peace negotiations.
The bitter rift between Fatah and Hamas goes back to the start of limited Palestinian self-rule in the 1990s, when strongmen of the secular Fatah cracked down on the Islamist militant group.
Tensions jumped during the last parliamentary elections in January 2006 when Hamas, running for the first time in a national ballot, unexpectedly routed the long-dominant Fatah.
Hamas grabbed 74 seats in the 132-member parliament, leaving Fatah with 45.
Simmering divisions boiled over in June 2007 when Hamas fighters expelled Abbas loyalists from Gaza in a week of bloody clashes, seizing control of the impoverished and densely populated territory.
Egypt has unsuccessfully tried for months to get the bitter rivals to sign a reconciliation deal.
