The Trump administration's failure to appoint a US ambassador to Australia is being dubbed both a diplomatic insult and a blessing.

Former deputy prime minister Tim Fischer is of the view the appointment delay of more than 15 months is a snub and reflects Australia's low priority status in Washington DC.

"This is now bordering on a diplomatic insult," Mr Fischer said.

Mr Fischer believes tensions over the US refugee resettlement deal are to blame.

Prime Minister Malcolm Turnbull's personal relationship with US President Donald Trump got off to a rocky start with a heated phone call on the issue a year ago.

The ambassador posting has been empty since September 2016 with Charge d'Affaires James Carouso acting in the role.

There has been speculation Admiral Harry Harris who leads US Pacific Command would take up the role.

Former Australian diplomat Bruce Haigh said it's a blessing in disguise not to have a political appointee.

He said some of the Republican Party appointees to the role over the years had been dreadful.

"They're usually big party donors, I think one of them was a used-car salesman," Mr Haigh told AAP.

He said it was much better to be dealing with a professional US diplomat.

Acting Opposition Leader Tanya Plibersek said it was concerning Australia still doesn't have a full-time ambassador from the United States.

"It could be that it's just not top priority for the US administration," she said.

The Australia-US relationship is again under the microscope after The New York Times revealed Canberra's top envoy in the UK, Alexander Downer, helped spark an FBI investigation into Russia's role in the US election.

Meanwhile, despite tensions running high over North Korea's nuclear testing, South Korea has also been without a US ambassador for the past year.

Victor Cha, a university professor, has been nominated and his appointment is awaiting US Senate approval.