On the January 2, the 115th United States Congress will sit for a final time.

Most of the focus will be on the partial government shutdown.

At this stage, it looks highly unlikely President Donald Trump and Senate Democrats will strike a budget deal to get all federal agencies fully back open.

That will probably be a problem for the 116th Congress that will be sworn in with much fanfare the very next day.

But the Senate also has other outstanding business, including more than 150 nominations on its "Executive Calendar" that are yet to be approved.

The most significant name on the list, as far as Australia is concerned, is on the bottom of page 29 — Arthur Culvahouse Jr.

Mr Culvahouse was approved to become the next US ambassador to Australia by the Senate's Foreign Relations Committee in mid-December but there has been little movement since then.

If he is not formally endorsed by the full Senate before this Congress ends, his nomination will expire.

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It would mean Mr Culvahouse would have to go through the entire process of being nominated and confirmed again, potentially delaying his arrival in Australia.

The ambassador's position in Canberra has already been vacant since 2016.

Mr Trump, who has been in the White House firing barbs at his Democratic opponents on Twitter throughout this shutdown, tried to politicise the backlog of nominations.

"Heads of countries are calling wanting to know why [Democratic] Senator [Chuck] Schumer is not approving their otherwise approved Ambassadors!?" Mr Trump tweeted.

"These are people who have been approved by committees and all others. Very Unfair!"

It's worth noting there seems to be bipartisan support for Mr Culvahouse's appointment in the Senate, and the Democrats — who are in minority — have no control over the schedule anyway.

It's also not unusual for Congress to quickly and unanimously flick through their "to do" lists in their final sessions, meaning he could potentially be approved on Wednesday and on his way to Canberra within months.

But the long-vacant position has already been something of a sore spot in the Australia-US relationship.

Former politicians, like Kevin Rudd and Tim Fischer, have been particularly critical.

A further delay — even a small bureaucratic one — is unlikely to be welcomed by anyone Down Under.