Tulsi Gabbard - a former Democrat congresswoman who joined the Republican Party to back Donald Trump - is the president-elect's pick for director of national intelligence.
The wide-ranging role would mean she oversees US intelligence agencies like the CIA, FBI and the National Security Agency (NSA), which focuses on intelligence gathering.
The nomination has raised questions over Gabbard's lack of experience in intelligence as well as accusations that she has in the past amplified Russia propaganda.
She will require Senate confirmation to take up the role.
If she is confirmed to the role Gabbard would manage a budget of more than $70bn (£55bn) and oversee 18 intelligence agencies.
But the nomination has sparked criticism in some quarters.
Reacting to the appointment on X, Democrat Virginia congresswoman member of the House Intelligence Committee Abigail Spanberger said she was "appalled at the nomination of Tulsi Gabbard".
"Not only is she ill-prepared and unqualified, but she traffics in conspiracy theories and cozies up to dictators like Bashar-al Assad and Vladimir Putin," she said.
Who is Tulsi Gabbard?
A military veteran who served with a medical unit in Iraq, Gabbard has set a number of political precedents in her career.
She was first elected to the Hawaii State Legislature aged 21 in 2002, the youngest person ever elected in the state. She left after one term when her National Guard unit was deployed to Iraq.
Gabbard went on to represent Hawaii in Congress from 2013 until 2021 - becoming the first Hindu to serve in the House.
She previously championed liberal causes like government-run healthcare, free college tuition and gun control. These these issues were part of her 2020 run for the Democratic presidential nomination - which she eventually dropped out of, endorsing Joe Biden.
In 2022 she left the Democrat Party and initially registered as an independent - accusing her former party of being an “elitist cabal of warmongers” driven by "cowardly wokeness".
Becoming a contributor to Fox News, she was vocal on topics such as gender and freedom of speech and became an outspoken supporter of Donald Trump before joining the Republican Party less than a month ago.
Controversial remarks on Syria and Ukraine
In 2019, during Gabbard's bid to secure the Democratic presidential nomination she was criticised by rivals after receiving apparently favourable coverage on Russian state media.
In the same year, she also faced criticism for her perceived support of Syrian President Bashar al-Assad, seen as a key Russian ally.
She said Assad "is not the enemy of the United States because Syria does not pose a direct threat to the United States" - and defended meeting him in 2017, during Trump's first term.
In that same year, she said in an interview with CNN that she was "sceptical" that the Syrian regime was behind a chemical weapons attack which killed dozens of people.
Trump said there could be "no dispute that Syria used banned chemical weapons".
In 2019, Gabbard did also describe Assad as a "brutal dictator".
Gabbard has also made a strong of controversial statements relating to Russia and its full-scale invasion of Ukraine.
Writing on social media on the day Russia invaded, she said the war could have been prevented if had the US and its Western allies had recognised Russia's "legitimate security concerns" about Ukraine's bid to join Nato.
The following month, she said it was an "undeniable fact" that there were US-funded biolabs in Ukraine that could "release and spread deadly pathogens" as she called for a ceasefire.
In response, Republican senator Mitt Romney said Gabbard had embraced "actual Russian propaganda".
On Russian TV her nomination as intelligence director is being framed as likely to complicate Washington's relations with Ukraine.
Rossiya 1 correspondent Dmitry Melnikov said that her nomination "does not bode well for Kyiv", noting that in the past she "openly accused the Biden administration of provoking Russia".
The channel's presenter also pointed out that Gabbard had "strongly criticised Zelensky and called for dialogue with Russia".
Additional reporting BBC Monitoring's Francis Scarr