And the publication this week of "The Future of U.S.-China Relations Under Xi Jinping", written by Mr Rudd during a year at Harvard University, is being seen in some diplomatic circles as part of an undeclared job application process.

In an exclusive interview with Fairfax Media, Mr Rudd did not deny his interest in the job but said he took the "utterly pragmatic" position that it was Eastern Europe's turn to take over leadership of the United Nations when Secretary-General Ban Ki-Moon steps down on December 31, 2016.

Tensions over the Ukraine and an increased deployment of NATO forces to Eastern Europe mean that either Russia or the US could block a candidate.

But Mr Rudd said: "I'm sure across Eastern Europe there are those of more neutral persuasion. Who knows, we are 18 months away from that, but the bottom line is that the overwhelming consensus in the United Nations system is that it's a rotation to Eastern Europe. Therefore it is not applicable to yours truly."

"I'm just being utterly pragmatic about it, that's just the bottom line."

If an Eastern European candidate is blocked, Mr Rudd or New Zealand's former prime minister Helen Clark could stand as a candidate for the Western Europe and Others grouping.

Law professor, Jesuit priest and Rudd confidante Frank Brennan said the pair had discussed the role and "if the world looked to our part of the world, I'm sure he would have an interest".

"But as a mate I say to him, if it came to our part of the world, there is him and Helen Clark. But guess what, she is a woman [the UN has never been led by a woman], she is competently running a UN operation, the UN Development Program, and she wouldn't attract the same static from her own audience," he said.

Former Labor foreign minister Bob Carr said he had recently heard Mr Rudd had an estimated 25 per cent chance of claiming the job and that he was "proving already a more plausible candidate than his critics in Australia are prepared to believe".

"He is clearly working this as he worked the caucus ballot that lifted him into the leadership of the ALP; cultivating all the players, presenting his credentials everywhere required. Obviously the psychological motivation is pretty formidable."

Other former Labor colleagues who remain in touch with Mr Rudd confirmed his interest in the role and spoke of receiving phone calls and texts from global capitals at all hours of the day.

Rudd biographer Nicholas Stuart said it was "inconceivable that he would not desire to put his hat in the ring" but cautioned China could be the biggest stumbling block and could possibly veto him.

"He does speak Mandarin. He does have a great awareness of the communist party, and he knows many of these people personally ... but I don't think China would be willing to accept someone like that in a formative international organisation like the United Nations," he said.

Mr Rudd is effusive in his praise of Mr Xi in "The Future of U.S.-China Relations".

Mr Rudd's predecessor as Labor leader Kim Beazley, now Ambassador in Washington, has told colleagues in the diplomatic community the former prime minister is lobbying for the job.

In an otherwise expansive interview last December, Mr Beazley said he had no comment on the matter.

Mr Rudd's recent move with wife Therese to New York to serve as president of the Asia Society Policy Institute provides him with the perfect location to escalate his behind the scenes lobbying efforts.

New Zealand Prime Minister John Key has backed Ms Clark's possible candidacy but Foreign Minister Julie Bishop said last month Australia would "need to wait to see who puts their hand up to be considered as an applicant for the secretary-general's job. Of course, if an Australian were to indicate that they wanted to be the secretary-general of the United Nations, we would consider that at the time".

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