Mahmud Abbas's mandate as Palestinian president, disputed by Hamas, could be extended to avoid a constitutional vacuum, a Palestinian official said on Sunday.

"The PLO central committee will discuss the options to avoid a constitutional vacuum" at its meeting due to take place on December 15, Mohammed Dahlan told reporters in the West Bank town of Ramallah.

"One of them (the options) is the extension of the mandate of president Abbas," said Dahlan, a member of both the committee and of the Palestinian leader's mainstream Fatah party.

The Palestinian electoral commission said last Thursday that the elections called for January should be postponed because the vote can not take place in the Hamas-ruled Gaza Strip.

The election delay risks throwing the bitterly divided Palestinians into a legal and constitutional limbo, since the mandates of both president and parliament will have run out in January.

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 presidential decree as unconstitutional because his own mandate ran out last January.

Abbas was elected on January 9, 2005 for a four-year term. The Palestinian Authority extended his presidency by one year so presidential and parliamentary elections could be held on the same date, as required by Palestinian Basic Law.

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 unexpectedly routed the long-dominant Fatah.

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.

The Palestine Liberation Organisation (PLO), which groups the main nationalist factions, is recognised internationally as the "sole legitimate representative" of the Palestinian people, a status contested by non-member Hamas.