Gordon Brown promised that there would be "limits" on the privatisation of the National Health Service if he became Prime Minister.
As delegates gathered for the Labour Party conference in Manchester, the Chancellor set out his stall as Tony Blair's heir apparent.
In an interview for BBC1's Politics Show, he sought to reassure the big unions over his plans for the NHS.
He set out to placate his critics in the Cabinet, promising to pick a government of "all the talents".
And while he said that he would continue to stand "solidly" with America in the "war on terror", he also acknowledged that the issue would have to be approached in "new ways" in the years ahead.
Mr Brown again denied that he had plotted over the summer to oust Mr Blair. He said that his close ally, junior defence minister Tom Watson, had been wrong to sign a letter, along with a clutch of ministerial aides, calling on Mr Blair to go.
Mr Brown told the programme: "I knew nothing of that letter. I think it was a mistake".
The Chancellor insisted that he would welcome a contest for the leadership and indicated that he would seek to appoint a broadly-based government if he was elected.
On the health service he pledged that there would be limits to the involvement of the private sector.
"I think there are limits to the role of the private sector in the health service that we've set down as a Government because, essentially, the private sector is doing part of the job of the health service but not all of the job of the health service and I think most people would accept that."
