"It is very likely," Kerry said during an interview on the "CBS Evening News" Tuesday night when asked by host Scott Pelley if he thinks either nation is reading his email.

"Unfortunately, we're living in a world where a number of countries, China and Russia included, have consistently been engaged in cyberattacks against American interests, against American government," Kerry said, adding it's an issue of "enormous concern."

As for his own email, Kerry said he keeps the possibility in mind.

"It's very possible ... and I certainly write things with that awareness," he said.

NBC News reported this week that the government has determined Chinese hackers have been snooping on the personal email accounts of top U.S. officials since 2010.

Though the administration hasn't confirmed the private email intrusion, several of the highest-profile unclassified computer networks the government maintains were breached by hackers in the past year, including the State Department and White House.

Most recently, the Joint Chiefs responded to a breach of its unclassified email server, and the U.S. suspects Russian spies are behind it.

Kerry reiterated that the U.S. has raised concerns about cyberespionage with the Chinese in direct talks -- as the administration has said many times before. it is also sure to come up when President Barack Obama meets with Chinese President Xi Jinping in September.

"Spying has taken place for centuries, and the latest means of spying is to be going after peoples' cyber," Kerry said. "Companies spend billions of dollars to protect themselves, the United States government does the same. We are deeply involved in fighting back against this on a daily basis."

(CNN)