Australian Prime Minister Julia Gillard has announced a ballot for the Labor leadership and called on ex-leader Kevin Rudd, widely expected to challenge, to accept its outcome as final.
"I have decided that at 10:00 am Monday morning a ballot for the Labor leadership will be conducted," Gillard told reporters on Thursday, adding that she would re-nominate for the job and expected the full support of her Labor colleagues.
Were she to, against expectations, lose the ballot, Gillard said she would retire to the backbench and renounce any future claims to the leadership, and she called on Rudd to do the same.
"Australians are rightly sick of this and they want it brought to an end," Gillard said.
Earlier, Rudd said he was encouraged by support from government colleagues to challenge Gillard for party leadership.
Rudd told reporters at his hotel in Washington on Thursday that Gillard could not lead the party to an election victory next year.
But Rudd will not say whether he will challenge Gillard in a leadership ballot of Labor lawmakers until he returns to Australia on Friday.
He said: "I've had many conversations with caucus colleagues and with ministerial colleagues. I'm very pleased and encouraged by the amount of positive support that encourages me to contest the leadership of the Australian Labor Party.
"The simple truth is that I cannot continue to serve as foreign minister if I don't have Prime Minister Gillard's support," Rudd told a news conference late on Tuesday in Washington, where he had earlier attended a meeting of G20 foreign ministers.
Gillard, on her part, said she was disappointed by Rudd's resignation.
"I am disappointed that the concerns Mr Rudd has publicly expressed this evening were never personally raised with me, nor did he contact me to discuss his resignation prior to his decision," she said.
Speculation has been rife in Australia that Rudd is planning to reclaim the prime ministerial post almost two years since he was replaced by Gillard in June 2010 after losing the support of Labor Party leaders.
Gillard has refused to comment on those reports, saying she had already answered many questions about the leadership, while Rudd has dismissed the rumours as a "soap opera".
"I can promise you this: There is no way - no way - that I will ever be party to a stealth attack on a sitting prime minister elected by the people," Rudd said in his resignation speech, in a scarcely concealed dig at his successor.
"We all know that what happened then was wrong and it must never happen again."
Al Jazeera's Andrew Thomas, reporting from Sydney, said there was "intense speculation" in Australia following Rudd's resignation.
"He is still very sore about the way he was deposed," said our correspondent, referring to the way in which Gillard replaced him.
"Gillard's poll numbers have declined; meanwhile Rudd's poll numbers have remained quite high," he said, adding that many thought he stood a better chance at the leadership now.
Our correspondent said Rudd would travel back to Australia and was expected to make an announcement on Sunday, before parliament convenes on Monday.
Rudd became prime minister in 2007 after a landslide electoral win which ended more than a decade of conservative rule.
His sudden replacement by Gillard took most Australians by surprise, and there is still some sympathy among voters about the way he has been treated.
Gillard leads a fragile minority government after failing to secure Labor a majority at a 2010 election. She has struggled with unpopular policies and poor opinion poll ratings that suggest the party would be voted out of power were an election held tomorrow.
Gillard's deputy on Wednesday launched a scathing attack on Rudd's past record as prime minister and party leader, accusing him of "dysfunctional decision making" and a "deeply demeaning attitude" towards his colleagues.