President-elect Joe Biden is nominating former rival for the Democratic presidential nomination, Pete Buttigieg, as secretary of transport.
The decision leaves the former mayor of South Bend, Indiana, poised to become the first openly gay person confirmed by the Senate to a US Cabinet post.
The nomination will help Mr Biden to meet calls for further diversity in his Cabinet.
Mr Buttigieg, 38, would also add a young dynamic to an administration that is so far dominated in large part by leaders with decades of Washington experience.
"“Mayor Pete Buttigieg is a patriot and a problem-solver who speaks to the best of who we are as a nation," Mr Biden said.
"I am nominating him for secretary of transportation because this position stands at the nexus of so many of the interlocking challenges and opportunities ahead of us."
Mr Buttigieg had been rumoured to be a contender for several different spots in Mr Biden’s administration.
He was surprisingly competitive in the race for the Democratic presidential nomination this year, winning the first-in-the-nation caucuses in Iowa.
He became a leading figure in national politics but when Mr Biden took control of the race in February, he dropped out and endorsed him, helping to consolidate support for the moderate wing of the party.
The Human Rights Campaign, the nation's largest advocacy group for the LGBTQ community, praised the nomination, saying Mr Buttigieg "was open and honest" about his identity and gave a voice to the community.
"His voice as a champion for the LGBTQ community in the Cabinet room will help president-elect Biden build back our nation better, stronger and more equal than before," HRC president Alphonso David said.
Mr Biden and Mr Buttigieg became close during the primary, chatting before debates and other campaign events.
He was active in supporting Mr Biden's campaign on television in the election’s final weeks.
The president-elect has said that Mr Buttigieg reminds him of his late son, Beau, who was Delaware’s attorney general before dying from brain cancer at 46 in 2015.
“To me, it’s the highest compliment I can give any man or woman,” Mr Biden said in March. “Like Beau, he has a backbone like a ramrod.”
Mr Buttigieg will play a central role in shaping some of Mr Biden’s policies.
Mr Biden has pledged to spend billions making major infrastructure improvements and on retrofitting initiatives that can help the US to battle climate change.
He also wants to immediately make mandatory wearing masks on planes and public transport to slow the spread of the coronavirus.
Infrastructure spending can be a bipartisan issue, and President Donald Trump spent years promising to push a major bill through Congress, although it never materialised.
Instead, his administration moved to soften carbon emissions standards that Mr Biden’s team will probably work to undo as part of the broader commitment to slow global warming.
Despite having governed a city of barely 100,000, Mr Buttigieg was credited with changing traffic with his Smart Streets initiative, a three-year project to convert 12.9 kilometres of multilane roads into two-way routes that enhanced South Bend’s downtown.
The project received awards for environmental protection.
Though on a far smaller scale than the nation’s transport systems, the project, and Mr Buttigieg’s initiative to convert the city’s sewers to a smart-flow system, demonstrates what supporters have called his next-generation infrastructure vision.
