Finland, which shares a 1,340 kilometre (800-mile) border with Russia, joined the US-led alliance in April 2023, dropping decades of military non-alignment.

Only 32 percent of respondents trusted that NATO's security guarantees formed such a robust deterrent that no one would dare to challenge a member state militarily, according to the survey by the Finnish Business and Policy Forum (EVA).

That is fall of 21 percentage points from the autumn of 2023, when the same question was asked in an EVA survey.

"Trust in NATO's security guarantees is no longer as straightforward as it once was. Behind this change lies the election of Donald Trump as president of the United States," EVA said.

Sami Metelinen, managing editor at EVA, said in a press release that Trump's statements that NATO countries not spending enough on defence might not necessarily be defended "has not gone unnoticed by Finns".

A majority of 66 percent of Finns still view Finland's membership as something positive, but it was down five percentage points from a previous survey published in November and the lowest level since May 2022, when the country applied for membership after Russia's invasion of Ukraine.

The survey also showed that 53 percent did not believe membership guaranteed that other countries "would ultimately help Finland in a real crisis".

EVA said 2,070 people aged 18 to 79 took part in the survey, which was conducted in March.