Williams, who starts his new job in September, will be responsible for Arab-Israeli issues as well as Iran and Iraq, the Foreign Office said in a statement.
A former journalist and Foreign Office adviser, he has been U.N. special coordinator for the Middle East for less than three months.
In contrast with former prime minister Tony Blair’s personal Middle East envoy, Lord Michael Levy, Williams will report to both Foreign Secretary David Miliband and Brown, the Foreign Office said.
“His responsibilities will cover the wider Middle East including Iraq and Iran in addition to the Middle East peace process,” it said.
Rosemary Hollis, director of research at the Chatham House thinktank, said Williams was a “suitable choice” because of his knowledge of the issues, his experience and because he had moved in both British government and U.N. circles.
Brown’s government is expected to put the stress on economic development in Gaza and the West Bank, seeing this as an essential building block to peace in the Middle East.
Hollis said Williams will be able to draw on years of research carried out by Ed Balls, a close ally of Brown, on an “economic roadmap” for rebuilding the region’s economy.
In Iraq, British troops are gradually handing over security duties to Iraqi forces and speculation has been rife that Brown could speed up their withdrawal from the country.
On Iran, Brown and U.S. President George W. Bush agreed this week on the need to pursue tougher sanctions against the country over its nuclear programme.
CLASH WITH BLAIR?
Williams was appointed days after Brown returned from a visit to the United Nations where he met Secretary-General Ban Ki-moon and called for action to put the world back on track towards slashing extreme poverty by 2015.
The Guardian newspaper, which reported last month that Brown planned to appoint Williams, said it could lead to a clash with the work of Tony Blair, who Brown succeeded as prime minister in June.
The Quartet of Middle East mediators — the United States, United Nations, European Union and Russia — appointed Blair as an envoy. Blair and Brown, his long-serving finance minister, had a tense relationship during Blair’s decade in power.
In the 1990s, Williams served with the U.N. in Cambodia, the former Yugoslavia, Geneva and New York.
In July 2006 he was appointed special adviser on the Middle East to Kofi Annan. He played a critical role in the implementation of Security Council Resolution 1701 which ended the Israel-Lebanon war, the Foreign Office said.
Williams was appointed to his current post by Ban on May 15 and has played a key role relaying messages between Israel and Syria. He replaced Alvaro de Soto, whose farewell report said that U.N. policy in the region had failed because it was subservient to U.S. and Israeli interests.
