UNITED NATIONS (Reuters) - Tony Blair became the big-power Middle East envoy on Wednesday hours after he quit as Britain's prime minister, but faces a challenge winning Arab confidence having helped to invade Iraq four years ago.
His task will be to raise aid for the Palestinians, seek to build their ruling institutions and promote their economic development, said the Quartet of Middle East negotiators -- the United Nations, United States, European Union and Russia.
Blair, 54, replaces as Quartet envoy former World Bank President James Wolfensohn, who resigned in April of last year in frustration at the difficulty of making progress on a problem that has defied diplomacy for nearly 60 years.
In a statement, the Quartet said Blair, British premier for 10 years, had "long demonstrated his commitment on these issues" and would "bring continuity and intensity of focus to the work of the Quartet in support of the Palestinians."
"He will spend significant time in the region working ... to help create viable and lasting government institutions representing all Palestinians, a robust economy, and a climate of law and order for the Palestinian people," it said.
But as the White House hailed an appointment it championed, spokesman Tony Snow sought to lower expectations. "Tony Blair is not the person who comes in and says, 'A-ha, I will solve it,'" he said. "He's not Superman. He doesn't have a cape."
Some European diplomats have raised questions about Blair's ability to garner broad Palestinian and Arab public support because of his use of British troops in the U.S.-led invasion of Iraq and his close ties with U.S. President George W. Bush.
But Foreign Minister Bernard Kouchner of France, which opposed the Iraq war, welcomed his appointment, as did Bush, who said, "I am pleased that this capable man has agreed to continue his work for peace in the Middle East."
The Palestinian Hamas Islamist movement, shunned by the United States and its European allies after winning elections 18 months ago, sought to cast Blair as an ally of Israel.
"We do not expect Blair's role to be fair in any issue relating to the Palestinian-Israeli conflict or any other Arab-related cause," Hamas official Ghazi Hamad said.
An Israeli official said, "We think that Prime Minister Blair is very involved, understanding and will be a very positive influence on the Middle East peace process."
Blair himself acknowledged the difficulties of a peacemaking role meant to steer the Palestinians toward statehood after Hamas' violent takeover of the Gaza Strip.
"The absolute priority is to try to give effect to what is now the consensus across the international community -- that the only way of bringing stability and peace to the Middle East is a two-state solution," he said.
The task "will require a huge intensity of focus and work," he told Britain's parliament in a farewell appearance there.
Reports that Blair would get the job had gathered pace in recent days, with Russia, which has quarreled with Britain over a spy controversy in the past year, the last of the Quartet partners to give its assent.
The departing British leader spoke to Russian President Vladimir Putin by telephone earlier on Wednesday.
Blair faces a formidable task, with Israeli-Palestinian talks stalled for seven years against a background of the rise of Hamas, a string of Palestinian suicide bombings and rocket attacks against Israel, and harsh Israeli reprisals.
Washington wants to relaunch statehood talks with President Mahmoud Abbas, who opposes Hamas, in the occupied West Bank. But Israel, calling on Palestinians to first rein in militants, has resisted U.S. pressure to negotiate basic issues such as the fate of Jerusalem, Palestinian refugees and borders.
Supporters of Blair say he brings a patient and persuasive approach and point to his successes in crafting a deal between Protestant and Catholic parties in Northern Ireland.
"Tony Blair is not popular in those sections of the Arab world that are particularly hostile to the West," said Reginald Dale of the Center for Strategic and International Studies in Washington. "But that is not true of Arab governments, such as those of Jordan, Egypt or Saudi Arabia."
Additional reporting by Adam Entous in Jerusalem, Sophie Walker and Adrian Croft in London