China has boosted its efforts to influence the US presidential election in November and wants President Donald Trump to lose because it sees him as "unpredictable," a top US intelligence official said Friday.

"We assess that China prefers that President Trump -- whom Beijing sees as unpredictable -- does not win reelection," said William Evanina, director of the National Counterintelligence and Security Center.

"China has been expanding its influence efforts ahead of November 2020 to shape the policy environment in the United States, pressure political figures it views as opposed to China's interests, and deflect and counter criticism of China," Evanina said in a statement.

He pointed to China's criticism of Trump's handling of the coronavirus epidemic, of the US closure of China's Houston consulate, and of the US administration's stances on Chinese actions in Hong Kong and the South China Sea.

"Beijing recognizes that all of these efforts might affect the presidential race," Evanina said.

Evanina said Iran is using social media disinformation to divide the country and hurt Trump, while Russia is meddling to damage the campaign of his Democratic opponent Joe Biden.

"Russia is using a range of measures to primarily denigrate former vice president Biden and what it sees as an anti-Russia 'establishment,'" Evanina said.

"This is consistent with Moscow's public criticism of him when he was vice president for his role in the Obama administration's policies on Ukraine and its support for the anti-Putin opposition inside Russia," he said.

Evanina, the top intelligence official monitoring threats to the election, gave no details on the outside interference.

A strong hacking and social media campaign by Russia in 2016 is credited by US intelligence with helping Trump to victory over Democrat Hillary Clinton.

"Foreign efforts to influence or interfere with our elections are a direct threat to the fabric of our democracy," he said.