The US has alleged that Russia covertly spent more than $300 million since 2014 to influence politicians in over 24 countries, the media reported on Wednesday.
The Department of State's allegation is based on a declassified intelligence assessment released on Tuesday, the BBC reported.
According to a senior official from President Joe Biden's administration, "this is just the tip of the iceberg".
American intelligence "assesses that these are minimum figures and that Russia likely has transferred additional funds covertly in cases that have gone undetected", the official said during a phone briefing.
The intelligence assessment released in a cable did not name specific countries or officials believed to have been targeted by Russia, but said they spanned four continents, reports the BBC.
The administration official said the intelligence community was now privately briefing select countries on the alleged Russian covert financing, adding that the briefings would remain confidential.
Fictitious companies were said to be used to fund European parties and to buy influence elsewhere.
The Russian authorities have so far made no public statements on the US claim.
Moscow has previously blamed America's CIA intelligence agency for interfering in other countries' affairs, including by backing various coups around the globe, BBC reported.
The US has meddled in foreign elections more than 80 times worldwide between 1946-2000, not including coups or attempts at regime change, according to a database kept by Carnegie Mellon University researcher Dov Levin.
On Tuesday, State Department spokesman Ned Price called Russia's alleged covert funding an "assault on sovereignty".
Last year, US intelligence officials assessed in a report that Russian President Vladimir Putin was likely to have authorised attempts to influence the 2020 election in favour of former President Donald Trump.
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But it said no foreign government had compromised the final results.
Russia called the allegations "baseless".
