"If he gets this job with the Quartet, I would expect him to step down," John Burton, his agent, said.Final appearance
At his final appearance to in parliament, Blair was asked what he would do if he was given the role with the Quartet.
"Blair has been made a scapegoat for British foreign policy regarding Iraq"
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"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.
He said a Palestinian state would need to be "not merely viable in terms of its territory but in terms of its institutions and governance".
Members of the Quartet - the United States, United Nations, European Union and Russia - met in Jerusalem on Tuesday to discuss the appointment for which he is the only candidate.
The group is reportedly waiting for a final decision from Russia.
A spokesman for Blair's Downing Street office said on Tuesday said: "It is by no means a done deal yet."
But a US official who asked not to be named told the Reuters news agency that Blair was expected to be named as early as Wednesday .
"It is in the final stages of consultation all around," he said.Brown takes power
Brown, who as leader of the majority party in parliament will be asked to form a new government later on Wednesday, will be the first prime minister to take power without an election being held for 17 years.
The finance minister took over as Labour party leader on Sunday.
The two men entered parliament together in 1983, once shared an office and were the chief architects behind the restyling of Labour, but their friendship soured as Brown believed Blair had reneged on a deal to hand over the leadership sooner.
Blair became prime minister in 1997 after Labour won the biggest parliamentary majority for half a century with a strong public mandate for change.
But his popularity ratings dropped considerably, partly because of his decision to join the US-led invasion of Iraq in 2003 and support for the so-called "war on terror".
In an interview with The Sun
newspaper published on Wednesday, George Bush, the US president, rejected the allegation that Blair was an uncritical "poodle" to the US.
"He's bigger than that. This is just background noise, a distraction from big things. This kind of thing is just silly ridicule and that's how I treat it," he said.