"Blair isn't a welcomed character because he has never been authentic to the Palestinian aspirations to end the occupation and free prisoners from Israeli jails," Hamas spokesman in Gaza Fawzi Barhoum said.

"Blair has always worked under the American umbrella and he was behind wars and disasters which are still going on in Iraq, Somalia, Afghanistan and Lebanon," said Barhoum.

UN spokeswoman Michele Montas earlier announced the appointment of Tony Blair as the representative of the Quartet which also groups the United States, the European Union and Russia.

She said Blair was tasked with mobilizing world assistance for the Palestinians.

The nomination came shortly after Blair stepped down as prime minister and was succeeded by British Finance Minister Gordon Brown.

Barhoum accused Blair of "defending Israel's crimes against the Palestinians and supporting it against our people."

He said he didn't expect that Blair in his new position as the Quartet envoy "would play a fair role to end the Palestinian cause. "

However, Salam Fayyad, prime minister of Palestinian emergency government, told reporters that Tony Blair would be "an important addition to the framework of international dealings with the Palestinians through the Quartet."

Earlier Wednesday, Russian Foreign Minister Sergei Lavrov, whose country is a major Quartet member, told a joint news conference in Ramallah with President Mahmoud Abbas, "the decision will be announced later today."

Lavrov noted that "the Quartet had agreed on a mandate for a new envoy" but didn't give more details.

"Russia, as a member of the Quartet, is doing all it can to help the Palestinians regain unity," he said.

He added that Russia would participate in humanitarian aid to the isolated Gaza Strip, calling on Israel to take "additional steps and create an atmosphere to help the peace process."