Prime Minister Tony Blair said on Thursday he would quit within a year but refused to give an exact date to placate Labour Party mutineers who want a speedy change of leader to revive their fortunes.
He said that this month's Labour conference would be his last as leader.
But in a televised statement, he said: I'm not going to set a precise date now, I don't think that's right. I will do that at a future date and I'll do it in the interests of the country.
Chancellor Gordon Brown, eager to heal damaging divisions in the ruling party, said earlier he would support Blair's decision.
Brown, whose relationship with Blair has at times been strained over the years, stressed that it was for the embattled premier to decide when to go.
Blair's popularity has tumbled in opinion polls after government scandals over sleaze and mismanagement were compounded by controversy over the wars in Iraq and Lebanon. Some former supporters urgently want a change at the top.
Labour holds its annual conference later this month in Manchester and party members had been clamouring to know whether it will be Blair's last.
Blair has ruled the country for almost a decade and won three consecutive elections but with support ebbing away, his decline mirrored the dramatic slide in Margaret Thatcher's fortunes at the end of her premiership.
With party colleagues running scared about Blair's growing unpopularity and losing their jobs at the next election, a junior minister and seven government aides quit on Wednesday after calling on him to step down now.
Blair had already pledged he will not stand at the next election, expected in 2009.