WASHINGTON: The head of the FBI said Tuesday that China is pushing its preferences in the US election as part of broad intelligence operations, whose economic impact he called unprecedented.

Christopher Wray, director of the Federal Bureau of Investigation, did not say whether China backed either President Donald Trump or his presumptive Democratic rival Joe Biden, both of whom have harshly criticized Beijing.

"China's malign foreign influence campaign targets our policies, our positions, 24/7, 365 days a year," Wray said at the Hudson Institute.

"So it's not an election-specific threat; it's really more of an all-year, all-the-time threat. But certainly that has implications for elections and they certainly have preferences that go along with that."

US intelligence concluded that Russia intervened in the 2016 election, in part by manipulating social media, in an effort to elect Trump.

The Republican has criticized the 2016 finding and his administration has shown irritation over intelligence briefings that Russia is similarly interfering this year.

Wray was answering questions after a speech focused mostly on China's alleged economic espionage, cases of which he said have soared by 1,300 percent over the past decade.