The top US counterintelligence official on Friday warned that Russia, China and Iran will all try to interfere in the 2020 presidential election, with Russia already trying to undercut Democratic candidate Joe Biden.
In an unusual public statement, William Evanina, director of the National Counterintelligence and Security Center, said the three countries were using online disinformation and other means to try to influence voters, stir up disorder and undermine American voters' confidence in the democratic process.
"It would be difficult for our adversaries to interfere with or manipulate voting results at scale," Evanina said.
Multiple reviews by US intelligence agencies have concluded that Russia acted to boost Trump's 2016 campaign and undercut his rival Hillary Clinton's chances in that election.
Evanina warned on Friday that Russia is already going after former Vice President Biden and what it regards as an anti-Russia US "establishment."
He said his agency assessed that China would prefer that Trump not win re-election, because Beijing regards him as too unpredictable.
Evanina said Iran is likely to use online tactics such as spreading disinformation to discredit US institutions and President Trump and to stir up US voters' discontent.