By AJ Vicens

(Reuters) - U.S. officials have added a ninth telecommunications company to the list of entities compromised by a sweeping Chinese-linked cyberespionage operation known as Salt Typhoon, a top White House official said Friday. 

Anne Neuberger, the U.S. deputy national security advisor for cyber and emerging technology, told reporters on a call that the unnamed telecom was added to the list after the U.S. government shared guidance on how to detect and defend against the operation. Officials have previously alleged that the attackers targeted Verizon, AT&T, Lumen and others. 

The Cybersecurity and Infrastructure Security Agency on Dec. 18 urged senior government and political figures to move mobile communications to end-to-end encrypted apps as a result of the Salt Typhoon campaign, which has targeted officials associated with the campaign of former Democratic presidential candidate Kamala Harris and President-elect Donald Trump and Vice President-elect JD Vance, according to reports.

Officials have said "a large number of Americans' metadata was taken" as part of the campaign.

Chinese officials have previously described the allegations as disinformation and said Beijing "firmly opposes and combats cyber attacks and cyber theft in all forms."

Sen. Ben Ray Lujan, a Democrat from New Mexico, called Salt Typhoon the "largest telecommunications hack in our nation's history" during a Dec. 11 hearing, while Texas Republican Sen. Ted Cruz said the U.S. "must plug any vulnerabilities in communications networks." 

Federal Communications Commission Chairwoman Jessica Rosenworcel said Dec. 5 her agency was proposing rules requiring telecommunications carriers to secure their networks in light of the Salt Typhoon revelations.

Neuberger said Friday that the "Chinese gained access to networks and essentially had broad and full access," giving them the capability to "geolocate millions of individuals, to record phone calls at will," and that updated FCC rules could help limit the scope and impact of future intrusions.

(Editing by Chizu Nomiyama)