Britain's new leader chose his senior circle of ministers on Thursday, picking David Milliband, the youngest foreign secretary in decades and a rising star who voiced doubts over the Iraq war.

Milliband, a 41-year-old environment chief, was confirmed as Foreign Secretary, according to a British government official who spoke on condition of anonymity in line with government policy.

Gordon Brown, who became prime minister Wednesday after waiting for a decade, plans to offer roles to opposition legislators, according to reports and officials, part of sweeping changes to break with Blair's era.

Brown's spokesman, Michael Ellam, declined to comment in advance of a full announcement.

The 56-year-old Scotsman was making a host of appointments, replacing Britain's home secretary, health secretary and appointing his own replacement as Treasury chief.

Miliband replaces Margaret Beckett, who was packing her office Thursday after little more than 12 months as Britain's chief diplomat.

Miliband was pressed by some Blair loyalists to run against Brown to succeed Blair, but chose instead to back the new premier.

He pushed Blair, along with ex-Foreign Secretary Jack Straw, to take a tougher line with Israel over last year's conflict in Lebanon. Aides claim he also expressed private reservations over the Iraq war, though Miliband voted to authorize military action in 2003.

Appointing the youthful minister would be seen part of Brown's efforts to win back the trust of voters who bitterly opposed the U.S.-led conflict.

Much like new French President Nicolas Sarkozy, Brown also was seeking to offer roles to opposition legislators and leading business figures.

British media reported that Chris Patten, an opposition Conservative who was the last British governor of Hong Kong, and Baroness Shirley Williams, a Liberal Democrat peer and war critic, would be offered junior posts.

Alan Sugar, a business mogul who stars in Britain's version of "The Apprentice" TV show, would be made an adviser, British media reported.

"I will build a government that uses all the talents," Brown told reporters Wednesday.

Alistair Darling, the current trade and industry secretary — and another Scotsman, is widely expected to be named new Treasury chief.

Blair departed Wednesday to rousing applause and tears from lawmakers. He said he was sorry for the perils faced by British troops in Iraq and Afghanistan, but gave no apology for his decisions to back the United States in taking military action.

"I wish everyone — friend or foe — well," Blair said before departing the chamber to cheers. "And that is that. The end."

Blair later took a train to northern England — carrying his own luggage — where he told officials in the town he represented in Parliament he would resign as a British legislator.

He takes on a daunting role as envoy to the Quartet of Mideast peace mediators after presiding over a decade of rapid social change — and rancor at the Iraq invasion.

Having departed the Treasury for Buckingham Palace in a modest sedan with wife Sarah, Brown swept back to Downing Street in a sleek prime ministerial limousine.

"I remember words that have stayed with me since my childhood and which matter a great deal today — my school motto — 'I will try my utmost'," Brown told reporters.

President Bush was the first world leader to offer his congratulations in a phone call soon after Brown's appointment, Downing Street said.

Their 10-minute talk was "cordial and constructive," Ellam said, declining to specify if the leaders discussed Iraq.

Brown also held brief telephone chats with Sarkozy, Irish leader Bertie Ahern, German Chancellor Angela Merkel and Italian chief Roman Prodi.

In London, Brown continued discussions map out his legislative agenda seeking to head off the challenge from a revived opposition Conservative party. Polls already point to a "Brown bounce," with one survey putting his Labour party ahead of its rivals for the first time since October.

Most closely watched will be Brown's policy toward Iraq. British troop numbers there have rapidly fallen during 2007.

Blair left his successor an option to call back more of the remaining 5,500 personnel by 2008 — an opportunity likely to be grasped by a leader with a national election to call before June 2010. Brown confirmed Wednesday the number soon will fall to 5,000.

The succession of Brown ended a partnership at the pinnacle of British politics that began when he and Blair were elected to Parliament in 1983 — sharing an office and a vision to transform their party's fortunes.