The United Nations, the United States, the European Union and Russia have named Britain's Tony Blair as a Middle East envoy.
The group, known as the Middle East Quartet, announced the appointment hours after Mr. Blair stepped down as prime minister on Wednesday.
The Quartet's statement said recent events in Gaza and the West Bank make it more urgent than ever to advance the search for peace in the Middle East.
In his final appearance before the House of Commons as prime minister, Mr. Blair said the absolute priority in the Middle East is reaching a two-state solution to the Israeli-Palestinian conflict.
President Bush, released a statement welcoming Mr. Blair's appointment, saying the former prime minister will help Palestinians develop political and economic institutions they will need for a democratic, sovereign state.
The Quartet issued a "road map" to Israeli-Palestinian peace in 2003. Little progress has been made on its implementation.
The Palestinian militant group Hamas this month seized control of the Gaza Strip in fighting with Palestinian President Mahmoud Abbas' Fatah faction. Mr. Abbas responded by dismissing the Hamas-led government and installing a new one without the militant group. Fatah remains the main power in Palestinian-controlled areas of the West Bank.
Israel, the United States and the European Union have moved to bolster Mr. Abbas in his struggle with Hamas.