Kevin Rudd faces an uphill battle to nudge Helen Clark out of the way and become United Nations secretary-general, but he should not be counted out.

That is the view of one the United Nation's best known analysts.

Richard Gowan, a UN expert at the European Council on Foreign Relations, believes if the Australian cabinet approves former Australian prime minister Kevin Rudd's bid for the prized role a path to success could open up.

Mr Gowan said tit for tat vetoes of candidates, including former New Zealand prime minister and frontrunner Miss Clark, by UN Security Council permanent members the US, UK, Russia and China could lead Mr Rudd to victory.

"The US is generally believed to be backing an alternative candidate, Argentinian foreign minister Susana Malcorra, while the UK has given Helen Clark its early backing," Mr Gowan told AAP on Monday.

"Rudd will have to explain why Australia's two main western allies are supporting other people.

"Equally, the fact that the US and UK are apparently behind Malcorra and Clark might play to Rudd's advantage down the road.

"There is a good chance Russia or China will veto the leading western candidates early on, allowing Rudd to step up."

Russia has been insisting on the election of an Eastern European candidate while China has not given much away about its preferred candidate.

Key to Mr Rudd's hopes of succeeding South Korean career diplomat Ban Ki-moon could be China.

"If there is any hint that China votes to discourage Rudd in the upcoming UN straw polls his candidacy is in a lot of trouble, because his command of Mandarin and close contacts in Beijing are meant to be his greatest strength," Mr Gowan said.

One of Mr Rudd's disadvantages is the widespread sense at the UN that he has "tepid" support in Australia.