Former congresswoman Tulsi Gabbard's controversial 2017 meeting with Syrian leader Bashar al-Assad and past statements on Russia's invasion of Ukraine have drawn fresh scrutiny after President-elect Donald Trump picked her to oversee America's spy agencies.

If confirmed as US director of national intelligence (DNI), Gabbard would act as a steward of the nation's most important secrets, oversee 18 US spy agencies and serve as a close adviser to the president.

But former US national security officials and lawmakers have raised concerns that the choice of Gabbard - a fierce opponent of America's involvement in foreign wars and whom critics accuse of echoing Kremlin narratives - could negatively affect intelligence co-operation.

Lewis Luken, a retired diplomat who served as the deputy chief of mission at the US embassy in London during the first Trump administration, told the BBC that Gabbard's "dubious judgement" could give allies "reason to question how safe it is to share intelligence with the US".

Gabbard, who recently joined the Republican Party, has previously said her detractors are "warmongers" who seek to smear any critic of Washington's establishment.

Trump has also defended his pick, saying that Gabbard - a lieutenant colonel in the Army Reserve who deployed to Iraq and Kuwait - “will bring the fearless spirit that has defined her illustrious career to our intelligence community”.

But in an odd twist for a DNI appointment, Russian state media praised the Gabbard choice, which only added to the alarm among national security officials in the US capital.

Prominent talk show host Olga Skabeyeva said on 14 November that "virtually from the first days of Russia's special operation in Ukraine, she [Gabbard] explained its reasons, criticised the actions of the Biden administration, and also personally met none other than Syrian President Bashar al-Assad and supported his fight against terrorists."

For as long as she has been in politics, Gabbard's positions have earned her praise and scorn from Democrats and Republicans alike.

Her views have been generally anti-war, opposed to American intervention and deeply critical of the US intelligence community.

But it was her January 2017 "fact-finding" trip to Syria as a congresswoman that first sparked outrage - particularly when she later raised doubt about the US intelligence assessment that Assad's forces had used chemical weapons on civilians.

After the Trump administration launched a series of strikes on Syria in April that year following a chemical attack that killed more than 80 people, Gabbard called the strikes "reckless and short-sighted", saying they would escalate the civil war and hamper the collection of evidence about what had happened.

The US launched missiles at a Syrian Air Force base where the Pentagon said a warplane had taken off before dropping bombs filled with the nerve agent sarin on the rebel-held town of Khan Sheikhoun.

A UN panel later came to the same conclusion as the US, saying it was confident that the Syrian government was responsible for the release of sarin in the town.

Assad's government and its ally Russia rejected the report and alleged that the Syrian Air Force strike hit a rebel depot full of chemical munitions.

Gabbard's comments, and her controversial meeting with Assad, hung over her run for the Democratic presidential nomination in 2019.

Defending her actions, she told an interviewer that Assad, who is also backed by Iran, was "not the enemy of the United States because Syria does not pose a direct threat to the United States".

The Trump transition team has not responded to a request for comment from the BBC.

She drew further attention during Russia's full-scale invasion of Ukraine in 2022, when she made statements seen by some as echoing Putin's justifications for the war.

Gabbard said that the war could have been avoided if the Biden administration and the Nato military alliance "had simply acknowledged Russia’s legitimate security concerns" about Ukraine eventually becoming a member.

Weeks later, she released a video commenting that US-funded biolabs in Ukraine could be breached and "release and spread deadly pathogens". It came as Russia, defending its invasion, spread unevidenced claims that the US was helping Ukraine to develop biological weapons.

In response, Republican Senator Mitt Romney posted on social media that Gabbard was "parroting false Russian propaganda" and spreading "treasonous lies". Gabbard sent a cease-and-desist letter to Romney over his remarks.

And during the 2024 presidential campaign, Gabbard alleged that Vice-President Kamala Harris was the "main instigator" of the conflict in Ukraine for having supported Kyiv's Nato aspirations.

Nikki Haley, Trump's UN ambassador during his first term and a politician who challenged him for the Republican nomination in the 2024 election, said recently that Gabbard could not be entrusted with such a high-level intelligence role.

“This is not a place for a Russian, Iranian, Syrian, Chinese sympathiser,” Haley said.

Some worry that Gabbard taking the position could affect trust between US intelligence agencies and their foreign counterparts.

A former senior White House official said Gabbard's appointment could have "real effects on our ability to have intelligence diplomacy with close allies".

"It certainly will raise real questions in the minds of foreign counterparts if the person sitting across from them - Tulsi Gabbard - has fundamentally differing assumptions about Bashar al-Assad and Vladimir Putin," the official told the BBC.

A former Nato official in London echoed that concern, saying that Gabbard's nomination would raise serious questions about how the UK and other American allies approach the US intelligence community under Trump.

"I think there's an extreme level of discomfort because why would you appoint somebody who has got no background and wacky views to such a responsible position?" the former official said.

But others did not expect any change to their country's intelligence relationship with the US.

Duncan Lewis led Australia's domestic spy agency - the Australian Security Intelligence Organisation - through the early years of the first Trump administration. He said he did not know Gabbard, but stressed that the Australian-American alliance was more powerful than any individual.

"Our bilateral security relationship is strong and long-standing, and I expect that to continue," he told the BBC.

Each morning the DNI oversees what is included in the president's daily briefing, giving them power to shape the US leader's perceptions of the world and its threats.

That is something that US senators will keep in mind when they consider Gabbard's nomination, and that is what could make her Senate confirmation process contentious.

Elissa Slotkin, a former CIA officer and Democrat who served with Gabbard in the House of Representatives, told media outlet Puck that Trump's DNI nominee "has expressed views that seem to preference adversaries".

"Certainly, it gave me pause, when I heard the nomination," added Slotkin, who will vote on Gabbard's confirmation as a newly-elected Michigan senator.

James Lankford, a Republican who serves on the Senate Intelligence Committee, has said that he and other senators will have many questions about Gabbard's past comments, and the Assad meeting.

But another Republican senator, Eric Schmitt of Missouri, said some of the criticism of Gabbard from Democratic colleagues - including that she was "compromised" - had been "totally ridiculous".

“It’s insulting. It’s a slur, quite frankly. There’s no evidence that she’s a asset of another country,” he told NBC.

And Republican Senator Markwayne Mullin said that Gabbard was a "solid choice", whom allies would find "extremely capable".

"There’s some questions on the Republican side; there’s some questions on the Democrat side," he told the BBC.

"What I’ve been telling everybody is just sit down and talk to her."

Additional reporting by Francis Scarr, BBC Monitoring

North America correspondent Anthony Zurcher makes sense of US politics in his twice weekly US Election Unspun newsletter. Readers in the UK can sign up here. Those outside the UK can sign up here.