US President Joe Biden is nominating former Senator Tom Udall as the next United States Ambassador to New Zealand.

The White House confirmed on Saturday (NZ time) that the former Senator for New Mexico, described in a statement as having a "long and distinguished career in public service", is Biden's pick to fill the vacant spot in Wellington. He will also take the Samoa Ambassador job.

It comes following Biden's participation in an informal APEC leaders retreat overnight hosted by New Zealand's Jacinda Ardern. Ardern and Biden also spoke on the phone on Friday ahead of both the meeting and announcement of Udall's nomination.

Udall, a Democrat who served in the Senate between 2009 and 2021 after 10 years in the House, succeeds Scott Brown in the role. Brown - a Donald Trump appointee - left the post in December to become the dean of the New England Law school. 

According to a biography provided by the White House, Udall is "a notable champion for the environment, for Native Americans, for government and election reform and for resolving international disputes peacefully, if possible".

He previously served as the Attorney General of New Mexico and as an assistant United States Attorney. 

Politico reports Udall as saying he's honoured to be "working with one of our closest partners and allies" during this "critical time". He said challenges facing the names were COVID-19, climate change and China. 

It was reported earlier this year that Biden had tapped former Republican Senator Jeff Flake for the New Zealand role, but Flake later denied that and has since been given the ambassadorship to Turkey.

Udall will still need to go through the usual nomination process, which requires getting confirmed by the Senate. Brown was confirmed in 2017 94 votes to four. 

Biden also nominated a number of other figures to posts around the world on Saturday, including to Bosnia and Herzegovina, and Botswana.

Kevin Covert has been acting as the Chargé d'Affaires at the US Wellington Embassy since Brown's departure.