Brown to launch leadership bid
Following Tony Blair's announcement that he will step down on 27 June, the process of selecting a successor begins - with Brown seen as the favorite.
Would-be contenders Michael Meacher and John McDonnell have yet to declare if they have enough support to mount a challenge against him. Brown praised the PM's achievements as "unique" and "enduring."
Brown is expected to set out his priorities for Britain during a tour of marginal constituencies in London and south east England.
Blair first told the Cabinet of his departure plans on Thursday, before traveling to his constituency to make a speech to party activists.
He acknowledged his government had not always lived up to high expectations but said he had been "very blessed" to lead "the greatest nation on earth".
Brown, who attended the Cabinet meeting, said of Blair that people would remember "how he led the country after 7 July, how he responded for the world after 11 September in America, how he responded to the tragic death of Princess Diana".
He said Blair's legacy would also be better public services and a strong economy adding: "At all times he tried to do the right thing".
Brown gave the first hint that under his leadership there may be a cooling in Britain's relationship with the US.
In an interview with this week's Time magazine, he was pointedly non-committal - talking only of the strong shared values and interests of Britain and America and his belief that they will endure.
He was asked if, after his meeting last month with the president, he believes President Bush is a man he can do business with. He replied: "President Bush is the elected leader of the American people. I was pleased to have the chance to talk to him ... I have over the years worked with different administrations ... And I think with both parties in America relationships are strong."
In the article Brown also warned against expectations of a 100-day policy blitz, saying he will have a wider focus on winning public support and enthusiasm. On Iraq, he said he accepted responsibility as a Cabinet member and admits there are lessons to be learned, but adds: "There will be no sense in which we seek to walk away from decisions we made."
Brown is unlikely to face a Cabinet-level challenge for the leadership.
But he could still face a challenge from one of two left-wing backbenchers - McDonnell and Meacher.
The pair met on Thursday as planned to see who had the most support, with the idea that the one with the least support stepping aside.
However a press conference after that meeting was cancelled, with the two saying their numbers of backers were "too close to call" and further clarification were needed, with a decision postponed to Monday.
Candidates need the signatures of 45 Labour MPs to enter a contest.