By Paul Reynolds World affairs correspondent, BBC News website

Mr Blair: seeking a two-state solution

Tony Blair faces a real struggle to make progress in his new and startling role as a Middle East envoy.

He faces a struggle because the issues are so intractable.

The appointment is startling because his decision to join the American invasion of Iraq and to support Israel in its war against Hezbollah last summer pits great swathes of Arab opinion against him.

He is seen in Israel as a "friend". This gives him credibility with the Israeli government, without which nothing can be done.

He has the ear of Mr Bush. That will carry weight in a region where power often outbids everything else. But it could also be a drawback if he is seen as being too close to Mr Bush. His proven skills as a negotiator over Northern Ireland give him a track record of success by any reckoning.

The question of Hamas

One major issue is whether he will seek to engage with Hamas, which controls Gaza after its violent takeover. Hamas has been excluded from talks because it does not recognise Israel and has not committed itself to non-violence and existing agreements.

A Hamas spokesman said that "the experience of our people with Blair was bad."

His main point of contact with the Palestinians will be President Mahmoud Abbas and the new government formed without Hamas, which won the elections last year. Palestinians of the Abbas grouping welcome the appointment.

The veteran Palestinian negotiator Saeb Erekat said: "President Abbas welcomes the nomination of Mr Blair as envoy of the Quartet...(and) has given the assurance that he will work with (him) to arrive at a peaceful solution on the basis of two states."

The Israeli Prime Minister Ehud Olmert's office said that Mr Olmert "believes that Mr Blair can have a favourable impact, in particular by helping the Palestinians develop solid governmental structures."

Mr Blair himself might see in this task the chance of balancing the criticism he has suffered over the invasion of Iraq with praise for trying to tackle this confrontation.

The Quartet

Mr Blair will report to the so-called Quartet - the US, the UN, the EU and Russia, whose 2003 road map to peace has been overtaken by events. Russia was not hugely enthusiastic at this appointment but is going along with it.

His mandate is, initially at least, to concentrate on helping the Palestinians, but it includes the right to "liaise with other countries... in support of the agreed Quartet objectives". These include an overall settlement. During his last appearance in Parliament, he spoke in ambitious terms about his hopes.

"The only way of bringing stability and peace to the Middle East is the two-state solution, which means a state of Israel that is secure and confident of its security, and a Palestinian state that is not merely viable in terms of its territory, but in terms of its institutions and governance," he said.

'Rarefied atmosphere'

It is not hard to find sceptics about this appointment. "I am flabbergasted," said Rosemary Hollis of the think-tank Chatham House in London, who is writing a book about Mr Blair and the Middle East.

There might be an element of giving him the job simply because he wants it so badly but beyond that, the game plan, if there is one, might be to try to out-manoeuvre Hamas and build up President Abbas Rosemary Hollis Chatham House

"It beggars belief on so many levels. It shows how the people behind this live in a rarefied atmosphere and have no concept of what is happening on the ground.

"It is not just the question of Iraq. There is a whole combination of factors. He had little enough influence as prime minister. How can he have more now?

Hamas says its experience of Mr Blair was "bad"

"There might be an element of giving him the job simply because he wants it so badly but beyond that, the game plan, if there is one, might be to try to out-manoeuvre Hamas and build up President Abbas."

Mixed record

The history of Middle East envoys and campaigners is a chequered one. The great negotiator Henry Kissinger invented the concept of shuttle diplomacy when he calmed the region down after the 1973 war. President Carter was also successful and his efforts culminated in the Camp David accords between Egypt and Israel in 1978.

Others have not been so fortunate. President Clinton thought he came close, also at Camp David, in 2000 with Yasser Arafat and Ehud Barak, but his efforts fizzled out.

More recently, the Peruvian diplomat Alvaro de Soto ended his time as the UN's own Middle East envoy (a post that, like that of the EU Middle East envoy, few people know exists) with a bitter and disappointed final report dismissing the Quartet as irrelevant and castigating the United States for bowing to Israeli pressure.

Mr Blair will not want to suffer the fate of the previous Quartet representative, the former head of the World Bank James Wolfensohn, who left in frustration in 2006 after only a year.