Quartet on the Middle East

The Quartet on the Middle East or Middle East Quartet, sometimes called the Diplomatic Quartet or Madrid Quartet or simply the Quartet, is a foursome of nations and international and supranational entities involved in mediating the Israeli–Palestinian peace process. The Quartet are the United Nations, the United States, the European Union, and Russia. The group was established in Madrid in 2002, recalling Madrid Conference of 1991, as a result of the escalating conflict in the Middle East. Tony Blair resigned as the Quartet's Special Envoy on 27 May 2015.

The initiative to establish the Quartet evolved following the outbreak of the Second Intifada in September 2000 and the futile cease-fire attempts that followed. On October 25, 2001, representatives of the EU, UN and the US and Russian governments met Palestinian leader Yasser Arafat and jointly expressed support for his policy of implementing cease-fire and security reforms in the Palestinian Authority. During the Israeli incursions into Palestinian areas in April 2002, the representatives of the same four entities met in Madrid and again called for implementation of cease-fire agreements brokered by the US government before. In the same meeting, they also agreed to transform their quadripartite cooperation into a permanent forum for follow-up of the Israeli-Palestinian peace process.

James Wolfensohn, the former president of the World Bank, was appointed Special Envoy for Israel's disengagement from Gaza in April 2005. He stepped down the following year because of restrictions in dealing with the Islamic militant group Hamas and the withholding of money from the Palestinian Authority, risking its collapse.

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