Australian Foreign Minister Kevin Rudd Wednesday denied he was planning to challenge Prime Minister Julia Gillard for the leadership, amid reports she is preparing to sack him.

Australia's Labor government has been torn by speculation about whether Rudd, who Gillard suddenly ousted as prime minister in mid-2010 but who remains hugely popular with voters, would mount a bid to return to the top job.

But the globe-trotting diplomat, currently in Washington, said his support remained behind Gillard.

"Can I just say, as I've said many times before, that we have a prime minister, I support the prime minister, and I intend to remain as foreign minister," Rudd said.

Rudd is due to return to Australia at the weekend, and The Australian newspaper said Gillard is so confident she has the support of Labor MPs she will call a leadership ballot on Tuesday to force Rudd to put his hand up.

"Cabinet ministers believe momentum has turned back towards Ms Gillard and a leadership ballot is now inevitable on Tuesday morning in Canberra," The Australian's political editor Dennis Shanahan wrote Wednesday.

If he loses, Rudd would be immediately sacked as foreign minister by Gillard and moved to the backbench, Shanahan added.

Gillard refused to comment on the report, saying she had already answered many questions about the leadership and telling reporters: "I really don't have much to add."

A spokesman for her office rejected the idea of a ballot on Tuesday. "The prime minister's position hasn't changed," he told AFP.

Labor has been wracked by internal divisions as Gillard struggles against unpopular policies and miserable polling that suggest the party would be unceremoniously dumped were an election held tomorrow.

As tensions mounted and a video of Rudd uttering expletives and losing his cool posted anonymously on YouTube went viral, former Labor leader Simon Crean called on the foreign minister to "put up or shut up".

The Australian said Labor figures believed the constant speculation needed to be ended once and for all and there was no room in the cabinet for both Rudd and Gillard, his former deputy.

"Just having him there has been destabilising," one unnamed minister told the newspaper's online edition. "It can't go on."

Rudd became prime minister in 2007, after a landslide electoral win which ended more than a decade of conservative rule. But he was ousted in June 2010 in a party-room vote after losing the support of Labor's factional leaders.