PM tells Rudd he's not high on agenda

Prime Minister Malcolm Turnbull has cut Kevin Rudd down to size.

Cabinet on Thursday will decide whether or not to back the former prime minister's bid to become United Nations secretary-general.

Foreign Minister Julie Bishop believes Mr Rudd is qualified, despite apprehension from some within the coalition.

Cabinet secretary Arthur Sinodinos admits the prospect "grates" with some of his coalition colleagues, with Treasurer Scott Morrison reminding Labor it didn't support Peter Costello for a similar job with the IMF.

"I believe that as the other candidates are former leaders, former prime ministers, former foreign ministers of their country, then he is qualified to be a candidate," Ms Bishop told the ABC.

Mr Turnbull said Mr Rudd's nomination would be considered by cabinet members, but he made something clear while addressing reporters in Cairns.

"While I know it's a matter of great interest in the media, can I just say this, with all due respect to Mr Rudd it isn't the most important issue confronting the cabinet of the Commonwealth of Australia at this time," he told reporters in Cairns.

Opposition foreign affairs spokeswoman Penny Wong said some coalition MPs who have questioned Mr Rudd's suitability for the role should consider the national interest.

"Sometimes nation is more important than party," she said.