JERUSALEM — The outgoing British premier will be named today as special envoy for the international diplomatic Quartet on the Middle East with a portfolio focused on Palestinian Arab economic and political reform, a senior American official said.

Members of the Quartet — America, the European Union, Russia, and the United Nations — will give their public blessing and announce that Prime Minister Blair has agreed to take the job in simultaneous statements from their capitals and New York, the official told the Associated Press.

The official, who insisted on anonymity because the statements are still being drafted, spoke after being briefed on a meeting of Quartet representatives held earlier yesterday in Jerusalem.

The Quartet gathering came a day after the Israeli, Palestinian Arab, Egyptian, and Jordanian leaders held a summit in a unified stance against Hamas and its stunning takeover of the Gaza Strip. Monday’s summit at an Egyptian resort on the Red Sea was meant to bolster the Palestinian Arab president, Mahmoud Abbas, whose Western-backed Fatah Party was severely weakened by the Hamas victory. The Hamas takeover has left the Palestinian Arabs with two governments — Mr. Abbas’s new Cabinet based in the West Bank, and the Hamas rulers of Gaza, who are internationally isolated.

Three American officials said Monday that discussions on naming Mr. Blair to the envoy post had been completed and the issue was on the Quartet’s agenda.

Mr. Blair himself did not rule out the idea yesterday.

“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 in London. “As I have said on many occasions, I would do whatever I could to help such a resolution come about.”

Deputy State Department spokesman Tom Casey would not discuss Mr. Blair’s prospects.

“They have talked about the idea … of having an envoy, having someone who would be available on behalf of the quartet to work on a variety of issues, including efforts to help support the development of Palestinian Authority institutions,” Mr. Casey told reporters.

The senior U.S. official said the Quartet had agreed on a job description for the special envoy position that Mr. Blair will assume shortly after leaving office today, the senior official said.