Tony Blair will head for a meeting of his constituency Labour Party on Wednesday amid speculation that he is preparing to stand down as a MP, his agent John Burton has said.
Mr Burton said that he expected Mr Blair would give up his seat in Sedgefield, County Durham, if - as expected - he is confirmed as the new international envoy to the Middle East.
"I think, if he gets the Middle East job, he will resign as an MP," he said.
US officials in Washington said Mr Blair would be named as special envoy for the international diplomatic Quartet on the Middle East on Wednesday, after he finally stands down as Prime Minister.
His appointment was discussed by representatives of the Quartet - the US, the United Nations, the European Union and Russia - at talks in Jerusalem on Tuesday.
Earlier, Mr Blair signalled his enthusiasm for the job at his last No 10 news conference.
"I think that anybody who cares about greater peace and stability in the world knows that a lasting and enduring resolution of the Israeli-Palestinian issue is essential," he said.
"As I have said on many occasions, I would do whatever I could to help such a resolution come about."
According to US officials, Mr Blair's new job will primarily involve helping the Palestinian Authority to build political institutions and will not - at least to begin with - involve direct negotiations between the Palestinians and Israelis.
The post is expected to be unpaid but will come with staff and logistical support from the Quartet, as did a previous similar position held by former World Bank chief James Wolfensohn.
