As Prime Minister Malcolm Turnbull agonises over whether to nominate Kevin Rudd for the United Nations, cabinet minister Christopher Pyne says it's a "second-order issue" and that he will ultimately support whatever decision his boss makes.

Thursday's cabinet meeting was so strongly divided over the decision – with some arguing the former Labor prime minister is sufficiently qualified but others questioning his character – that it gave the Prime Minister authority to make a "captain's call".

"Whether Kevin Rudd is our nominee for secretary-general of the UN is a second order issue," Mr Pyne, now the Defence Industry Minister, told the Today show on Friday morning.

"Cabinet spent most of its discussion yesterday on the royal commission in the Northern Territory, on budget repair and on our agenda for the next three years and quite frankly, the Prime Minister will make an announcement about that today and that will be the end of the matter one way or another."