Malcolm Turnbull has not asked his Liberal deputy to ready herself to be acting prime minister while he's in the US next week in case the under-fire Barnaby Joyce is not available to do the job.

If both the prime minister and deputy prime minister, Mr Joyce, are unable to take Australia's reigns, Foreign Minister Julie Bishop would ordinarily be next in line.

There is pressure on the Nationals leader to step aside or at least take leave rather than act in the top job amid ongoing scrutiny of his actions relating to an extramarital affair.

But Ms Bishop, who has plans to be overseas herself next week, said Mr Turnbull had not asked her to be available.

"I'm over in Kuwait (this week) with back-to-back meetings from very early in the morning to late at night and focusing on Australia's military intervention and humanitarian contribution to Iraq so it's not a matter that I'm focusing on," she told ABC radio on Wednesday.

"I am returning to Australia from Kuwait; I do have plans to be overseas next week - parliament is not sitting - if circumstances change then, of course, I would change plans."

However, she said her understanding was the usual arrangements would apply next week.