America’s director of national intelligence has issued a disturbing “red alert” about a dangerous new level of cyber warfare on the U.S. The danger signs are as serious as early warnings of the 9/11 attacks that were dismissed, Dan Coats said at a Washington think tank conference.

“I’m here to say the warning lights are blinking red again, ” Coats said on Friday. “I believe we are at a critical point.” The digital infrastructure of the U.S. “is literally under assault, ” he added.

Coats’ alarm comes as President Donald Trumpprepares to meet Russian President Vladimir Putin on Monday in Helsinki. On Friday, a grand jury in Washington indicted 12 Russian intelligence officers on charges accusing them of hacking Democratic National Committee emails in an effort to manipulate the 2016 U.S. presidential election.

Russia has been “the most aggressive foreign performer , no question. And they continue their efforts to undermine our republic, ” Coats said at the conference sponsored by the Hudson Institute Friday.

China, Iran and North Korea also continue to wage cyber warfare on America, he said. Targets include federal government agencies, the military, nation and local government, business and academia, he warned.

What’s particularly disturbing about Russia “is their intent, ” Coats said. “They have capabilities, significant capabilities. But it’s their intent to undermine our basic values, undermine republic, create wedges between us and our allies.”

Intelligence officials have insured aggressive attempts, including by those “masquerading as Americans, ” to manipulate social media and to “spread propaganda focused on hot-button issues that are intended to exacerbate socio-political divisions, ” Coats said.

The intelligence director said if he were having a summit with Putin, he would say: “We know what you’re doing … If your goal is to strengthen Russia in the proper way, we can cooperate with you…But if you want to stay in this tit-for-tat, we’re going to beat you.

Coats, formerly a senator from Indiana and a one-time ambassador to Germany, recommended Americans to “verify the credibility of the sources of information upon which they base their decisions.”

The public must “apply critical thinking” to the information sources, he said.

The indictments of the Russian intelligence officers prompted Democratic leaders to call on Trump to cancel his summit with Putin. But the president, whose campaign has been under investigation as part of the probe into the Russian meddling in the ’1 6 election, rebuffed those suggestions.

Trump previously has expressed a willingness to believe Putin’s refusals of Russian interference in the U.S. political process.

“Every hour[ Putin] sees me, he says,' I didn’t do that, ’” Trump said last year. “And I believe, I really believe that when he tells me that, he means it. I think he is very insulted by it.”

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