The OSCE, which monitors elections in many parts of the world, will only send a small team to observe the US polls in November due to the pandemic, it said on Saturday.
The news comes as the credibility of the American voting system faces its most serious threat in decades, fuelled by presidential rhetoric, fears over record mail-in voting due to the pandemic, worry about ageing machines, accusations of voter suppression and foreign interference.
"The safety concerns as well as continuing travel restrictions caused by the COVID-19 pandemic are creating challenges for all our election-related activities and particularly for the deployment of long- and short-term observers," Katya Andrusz, OSCE spokeswoman, told AFP.
As a result, she said no short-term observers would be deployed to monitor the election on the day.
She added the team for the elections on November 3 would consist of just 14 analysts and 30 long-term observers.
In a July report seen by AFP, the Organization for Security and Co-operation in Europe estimated it would be necessary to deploy 100 long-term observers to monitor the overall electoral process, and 400 short-term observers on the day.
The OSCE is an international organisation based in Vienna, and one of its core missions is to ensure elections go well in its 57 participating states which include the United States.
US President Donald Trump, who is campaigning for re-election, has repeatedly sowed doubts about the integrity of the November election, calling for mail-in ballots to be banned.
A tweet in May, in which Trump said there was "NO WAY" that mail-in ballots would be "anything less than substantially fraudulent", earned the president his first-ever fact check by Twitter, which labelled the post misleading.
In August, he said: "The only way we're going to lose this election is if the election is rigged."
His Democrat challenger Joe Biden has expressed fear that Trump may try to "steal" the election or not leave office if he loses.