RAMALLAH, West Bank, Feb 12 (Ali Sawafta/Reuters) - Palestinian President Mahmoud Abbas called on Saturday for elections before September, but rival Islamist group Hamas quickly rejected the move, underscoring a crippling division among Palestinians.

The election call came a day after protests in Cairo led to the overthrow of Egyptian leader Hosni Mubarak.

Abbas's Palestinian Authority said the spirit of change in Egypt should inspire Palestinians to unite.

The Palestinian leadership decided to hold presidential and legislative elections before September, senior Abbas aide Yasser Abed Rabbo told reporters.

It urges all the sides to put their differences aside, he said, referring to a bitter rivalry between Abbas's West Bank-based government and Hamas, which controls the Gaza Strip.

But a quick solution to the Palestinian divide seemed unlikely and Hamas spokesman Fawzi Barhoum said the Western-backed Abbas, who has served as president since 2005, lacks the legitimacy to make such a call.

Hamas will not take part in this election. We will not give it legitimacy. And we will not recognise the results, Barhoum told Reuters.

The groups disagree on the interpretation of Palestinian election laws and previous ballots were cancelled with the sides unable to reach a reconciliation deal.

Abbed Rabbo said the disagreements could be resolved in a new legislative council to be formed after the presidential and parliamentary elections.

Hamas won the last parliamentary election in 2006 and a year later routed Abbas's forces to seize control of the Gaza Strip.

Hamas's opposition to Abbas's peace moves with Israel is one of the issues keeping the factions apart.

US-sponsored peace negotiations between Palestinian and Israeli teams have faltered since being relaunched last year.

Abed Rabbo said that Saeb Erekat, the chief Palestinian negotiator in the recent round of talks, has tendered his
resignation, but Abbas has yet to accept it.

Erekat had recently come under fire after internal memos supposedly documenting negotiation sessions with Israel were leaked to the media. Some commentators faulted Erekat for making what they considered to be far-reaching concessions to Israel.

Abed Rabbo called on US President Barack Obama to step up efforts in helping to reach a Palestinian statehood deal.

(Additional reporting by Nidal al-Mughrabi in Gaza; Editing by Maria Golovnina)