President Joe Biden said Wednesday he gave Russian President Vladimir Putin a list of places he considered critical infrastructure in the United States, warning Russians not to attack them.

“I gave them a list. If I’m not mistaken, I don’t have it in front of me, 16 specific entities,” Biden said. “Sixteen defined as critical infrastructure under U.S. policy from the energy sector to our water systems.”

Biden spoke about his list for Putin during a press conference with reporters after his summit with the Russian president.

He warned Russia that the listed critical infrastructure in the United States was “off-limits” in future attacks.

“I talked about the proposition that certain critical infrastructures should be off-limits to attack. Period,” he said. “By cyber or any other means.”

Since Biden became president, incidents of cybercriminals unleashing ransomware attacks on infrastructure in the United States has increased — including an attack on the Colonial Pipeline and JBS Foods, the world’s largest meat producer.

But Biden did not say he threatened Putin with consequences if the cyber attacks continued.

“He knows there are consequences,” Biden said. “He knows I will take action.”

Biden repeated that “responsible countries” need to take action against cybercriminals within their borders, but did not successfully receive a firm commitment from Putin on the issue during his meeting with the Russian president.

Putin said during his press conference there were “constructive” talks about cybersecurity, but claimed most of the cyber attacks in the world came from the United States, not Russia.