WASHINGTON (Reuters) - A senior U.S. official who is among those working to evict alleged Chinese hackers from American telecom companies has a word of advice for his fellow Americans:

Use encryption.

During a call with reporters on Tuesday, Cybersecurity and Infrastructure Security Agency official Jeff Greene said Americans should know that "encryption is your friend" and that "our advice is to avoid using plaintext."

Although it is not the first time a senior American official has endorsed encryption, a data-scrambling technique that helps protect communications from snoopers, it is a stark break with previous government messaging.

Only a few years ago, FBI Director Chris Wray described strong encryption as "an urgent public safety issue" amid a push by law enforcement officials to mandate that tech companies water down the protections around digital communications.

Greene's call with journalists was held as the government issued guidance for combating allegedly Chinese intrusions into U.S. telecoms.

Washington has voiced increasing concern over Beijing's alleged efforts to burrow deep into U.S. telecommunications companies, including T-Mobile, and steal data about U.S. calls.

U.S. officials have previously alleged that the hackers stole telephone audio intercepts, along with a large tranche of call record data. Officials have said those records mainly concerned people in the Washington area.

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

Greene's advice to switch to encrypted calls and messaging - which is offered by apps such as Meta Platform's WhatsApp and the privacy-focused service Signal - is a sign that the agency believes that Chinese hackers may be lurking in telecom companies' networks for some time yet.

Greene, who serves as CISA's Executive Assistant Director for Cybersecurity, said as much when asked about a timetable for kicking the hackers out of America's telecom networks.

"It would be impossible for us to predict when we'll have full eviction," he said.