Downing Street is trying to play down remarks by the prime minister that it was "a mistake" to announce he was not standing for a fourth term.
Mr Blair referred to Iraq in a speech to the Australian Parliament
Tony Blair's spokesman said he had only meant it was a mistake to expect speculation on his future to end.
He said Mr Blair had been cut-off mid-sentence during the interview.
He spoke out after the prime minister told Australian radio "People kept asking me the question so I decided to answer it. Maybe that was a mistake."
The Conservatives and Liberal Democrats say his remarks have created "a lot of uncertainty".
Mr Blair, who is visiting Australia, New Zealand and Indonesia, was asked by an ABC Radio interviewer whether it had been "a strategic mistake" to announce his departure.
He said: "I think what happens when you get into your third term and you are coming up to your 10th year is that it really doesn't matter what you say, you are going to get people saying it should be time for a change or when are you going or who's taking over?
"You just get on with the job because this speculation, I think, would happen whatever decision you take.
"Now, it was an unusual thing for me to say but people kept asking me the question so I decided to answer it. Maybe that was a mistake."
'Date in mind'?
Mr Blair has insisted he will serve a full third term in office before resigning. But there has been constant speculation about when he will quit and hand over to Chancellor Gordon Brown.
BBC Political Editor Nick Robinson on Monday reported that the prime minister was understood to have a firm date in mind for his departure, but even his closest aides did not know when it was.
It is unlikely to be as soon as some Labour rebels are hoping.
The prime minister's official spokesman said any report that did not make that clear that Mr Blair had been interrupted during the Australian interview was "inaccurate".
"He was going to go on to say that he had hoped the pre-announcement would end the speculation, but he did not say the pre-announcement was a mistake," the spokesman said.
"The purpose of his original statement was to be honest with the electorate about his intentions. He was aware there would be speculation."
'Exit strategy needed'
Asked about Mr Blair's comments, Deputy Prime Minister John Prescott told the BBC: "He might mean it caused an awful lot of uncertainties once he said that, and that was a concern expressed by a number at the time."
But Mr Prescott said he did not think Mr Blair's announcement had been a mistake because it enabled a smooth transfer of power.
Conservative leader David Cameron said Mr Blair's comments had given rise to "a lot of uncertainty".
"Every organisation needs a succession plan and the government of Britain is no different," he said.
Liberal Democrat leader Sir Menzies Campbell also urged Mr Blair "to tell us his own exit strategy", saying his recent remarks added to the "current uncertainty and sense of drift".
"The issue now is not the interests of the Labour Party but the good governance of Britain," he said.
The prime minister turned his attention to global matters in a speech to the Australian Parliament in Canberra.
He said: "If we want to secure our way of life, there's no alternative but to fight for it.
"That means standing up for our values not just in our own country but the world over."
On the situation in Iraq he said: "If the going is tough, we tough it out. This is not a time to walk away but to have the courage to see it through."