The Islamist group Hamas said on Monday it was backing President Mahmoud Abbas's attempt to win more clout for Palestinians at the United Nations, the latest sign of a rapprochement between the political rivals.

The Palestinians are registered as an observer entity at the UN and Abbas wants to see them upgraded to a "non-member state" in a UN General Assembly vote on November 29, giving him access to other international organisations.

The decision by Hamas was unexpected. It does not recognise Israel's right to exist and has dismissed previous attempts by Abbas to promote the Palestinian cause on the diplomatic stage.

Abbas holds sway in the occupied West Bank. Hamas governs the Gaza Strip and has just fought a fierce, eight-day conflict with Israel.

After more than five years of deep divisions, the two main political forces in the Palestinian territories have shown signs this past week they were ready to resume unity talks - driven closer together by the Israeli assault on Gaza.

Israel launched its offensive to halt rocket fire out of the coastal enclave into its southern towns and cities. Abbas denounced the Israeli assault and dispatched a top official to Gaza in a show of solidarity with Gaza.

Once the fighting subsided, the rival factions announced they would release their respective political prisoners.

Hamas spokesman Sami Abu Zuhri said the group backed any political gain Abbas could achieve at the United Nations "without causing any harm to the national Palestinian rights".

Hamas political chief Khaled Meshaal, who lives in exile, told Abbas by telephone of his movement's change of heart, Hamas said in a statement.

Direct peace talks between Israel and Abbas broke down in 2010 over the question of Israeli settlement building in the West Bank and East Jerusalem - land the Palestinians want for their future state.

Hamas might struggle to explain its new position to some of its hardline supporters. As recently as Saturday, senior Hamas leader Mahmoud al-Zahar had urged Abbas not to go to New York.

Abbas's UN initiative "represents an ... official concession of the 1948 land," Zahar told reporters, referring to the year Israel proclaimed its independence following the end of British rule in the region.

While Hamas leaders accept the notion of a Palestinian state along lines established before the 1967 Middle East War, they say this should only be a transitional solution ahead of the eventual creation of a nation on the basis of 1948 boundaries.

Abbas has said he supports a two-state solution on the basis of the 1967 lines.

In his conversation with Abbas, Meshaal stressed the need for reconciliation between the two factions, especially in the wake of the Israeli offensive, which was ended thanks to a ceasefire deal brokered by Egypt.

"This signals that Hamas is showing greater flexibility towards reconciliation than any time before," said Gaza political analyst Hani Habib.

Speaking to hundreds of supporters in the West Bank city of Ramallah on Sunday, Abbas vowed he would speed up unity efforts after he returns from the UN vote.-Reuters