Malcolm Turnbull has played down the importance of Kevin Rudd's bid for the United Nations, fuelling speculation that cabinet could deny the request of the former Labor prime minister to be nominated to become Secretary-General.

"I know it's a matter of great interest in the media, can I just say 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," the Prime Minister said on Wednesday.

Mr Turnbull's cabinet, which meets on Thursday, is split over the request and few others than Foreign Minister Julie Bishop are prepared to argue for Mr Rudd.

Greg Hunt: "There are many, many people within our own party and the broader base of the party who will have their concerns." Supplied

Lower House independent Bob Katter said the government must back Mr Rudd, saying he was eminently qualified.

"To oppose Kevin Rudd's nomination would be seen as petty, partisan and political. None of which would bring respect to the government and would alienate the people's confidence, before the Parliament has even sat," he said.