Tony Blair intends to fight the next election as Labour leader, he told a tabloid newspaper on Saturday.
Mr Blair said he wasn't "going to go on and on for the sake of it".
He told the Mirror he believed in what he was doing and enjoyed the job.
But he said a guarantee he would finish a third term would sound "arrogant" and lead to headlines saying he would go "on and on" like Margaret Thatcher.
There has been speculation recently about the prime minister's future but senior ministers have repeatedly insisted he has no plans to step down.
Mr Blair told the newspaper he was "up for" fighting the next general election as leader.
"I don't feel that I am just going to go on and on for the sake of it.
"And whether I am prime minister after the next election is ultimately a decision for the British people," he told the Mirror.
Last week deputy prime minister John Prescott suggested Tony Blair could "follow the example of Harold Wilson" who stood down mid-term.
He said Mr Blair would have Labour's full support if he led the party into the next general election, but hinted that the prime minister could be derailed by "events".
The remark followed his earlier comments, which had suggested cabinet ministers were jockeying for position in case Mr Blair stood down.
A YouGov poll of 2,131 people published by the Daily Telegraph on Saturday suggested more voters believed Gordon Brown would make a better prime minister.
A total of 29% plumped for the Chancellor as the ideal candidate, while 25% opted for Mr Blair.
Is Gordon Brown more popular with voters?
The poll also said 59% believed Mr Blair should resign immediately or before the next general election - with 41% wanting him to step down immediately and 18%
preferring him to leave sometime ahead of the election.
Only 18% wanted him to stay for many more years.
During this weekend's interview Mr Blair said five-year plans about the party's future strategy would be unveiled before the summer holidays.
"It will set out the next stage of public service reforms, how we take our economy to a higher level and how we create a civic society with self respect and respect for others," he told the Mirror.
When asked if his Christian faith kept him going in his darkest moments he said: "Yes, absolutely."
On crime and anti-social behaviour he said the government wanted "decent ordinary law-abiding people to be in control of the streets, not the violent minority".
His reaction to the purple powder attack in the House of Commons recently was one of frustration he said, because he was "just about to land one on Michael Howard" and wanted to get on with the debate.