Caroline Kennedy, daughter of JFK and former ambassador to Japan, was named in reports by AP and Axios as a possible pick for the most watched diplomatic post in Canberra.

A spokesperson for the embassy says it cannot confirm who US President Joe Biden is considering for the position.

"We cannot comment, except to say that we are confident we will have a superb Ambassador, matching the enormous value we place in our Alliance with Australia," the spokesperson said.

"Consistent with normal diplomatic practice, any nominee would first receive agreement from the government of Australia."

The role has been vacant since former ambassador Arthur Culvahouse resigned one day ahead of the presidential handover from Donald Trump to Joe Biden on January 20.

Four months into his administration, Mr Biden is yet to announce any nominees for the highest profile ambassador appointments that are typically reserved for political allies.

The US Senate has been busy holding hearings and votes on the top administration roles including cabinet positions and deputy secretary and directorships of key agencies.

It is not unusual for ambassador positions normally reserved for political appointees to be left vacant for between three to six months into a new president's term, with top fundraisers to the presidential campaign often among those nominated.

Reports claim Mr Biden was expected to approach candidates with offers over the weekend, with the first slate of ambassadors as soon as this week.

Caroline Kennedy served in the role in Japan during Barack Obama's second term and was an early supporter of his presidential bid, along with her uncle, Ted Kennedy, helping him get an edge over Hillary Clinton.

Another Kennedy, Vicki, was on his radar for the representative to Western Europe, the reports claimed, both names are notable for not being large fundraisers to the Biden presidential campaign.

Other top diplomatic rumours include Eric Garcetti for the role in India, Rahm Emanuel for Japan, Ken Salazar for Mexico, Denise Bauer for France, Jane Hartley for Italy, David Cohen for Canada, and Cindy McCain, daughter of Republican senator John McCain, for UN envoy roles including leading the World Food Program.

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US State Department insiders say once the nominations begin, they'll come in batches.

The Australian nomination is expected to be made during the first round, but officials in the embassy in Canberra are not aware of when the news will come.

The announcement will be made by Mr Biden directly following private consultation with Australian government counterparts.

The ambassadorial appointments in Australia and New Zealand are considered of high importance due to the real work involved, both as Five Eyes countries and also their strategic importance in the Indo-Pacific region, which has been a priority focus for this White House.

Former US ambassador to Australia John Berry told The Canberra Times early in the year that the White House would take time to find a "high quality" nominee, as Mr Biden had made the Indo-Pacific a priority focus for his administration.

The two countries will mark 70 years of the ANZUS alliance this year, with Prime Minister Scott Morrison having invited Mr Biden to visit in 2021.

Political nominees rather than career diplomats are also expected in regionally significant countries of China, Singapore, Thailand, South Korea, Philippines, Japan and India, as well as the the US envoy to ASEAN.

A number of career diplomatic posts have already had nominations or had the existing ambassador remain in the role, such as the ambassadors to Indonesia and Malaysia. A career diplomat is awaiting confirmation as ambassador to Vietnam.

The ambassador to Pacific island countries including Fiji is typically a career diplomatic role, but the White House has kept that position open suggesting it may become a political appointment.

While waiting on an ambassador appointment, embassies are run by their second in command, known as the Chargé d'Affaires.

Chargé d'Affaires Michael Goldman is currently the top US embassy official in Canberra, having arrived in March last year.

The US embassy in Canberra is used to being run by the Chargé d'Affaires, with the top post left vacant for two years under the Trump administration.

The Biden White House is yet to name candidates for 345 senior administration positions, including ambassadorships, out of around 1200 that require Senate confirmation.

The administration is still working through nominations for administration deputy secretaries, undersecretaries and assistant secretaries which are all treated as political appointments requiring Senate confirmation, in what is considered one of the longest processes in any developed country for a new leader to appoint their top officials.

While the US Senate is currently tied 50-50 between Republicans and Democrats, with Vice President Kamala Harris providing the tie-breaking vote the White House has allowed the administration to move swiftly in filling positions.

Only one Cabinet candidate, in Neera Tanden at the Office for Budget Management, was withdrawn over difficulties obtaining Senate confirmation due to the volume of partisan comments on her social media accounts.

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