WASHINGTON, Jan 10 (Reuters) - The United States has

take steps in response to Chinese-linked cyber-espionage

operations against U.S. telecoms firms, U.S. national security

adviser Jake Sullivan said on Friday.

U.S. telecoms firms AT&T ( T ) and Verizon said late

last year their networks had been targeted by the cyber hackers,

but were now secure as they worked with the U.S. government and

law enforcement.

"We have taken steps in response to Salt Typhoon, in

response to Gold Typhoon, we have sent clear messages to the PRC

about what it would actually mean if they acted to disrupt

American critical infrastructure and how we would respond,"

Sullivan told reporters, referring to China by the initials of

its official name, the People's Republic of China.