Sanders told Russia is trying to help his campaign

It remains unclear how Russia is attempting to help Sanders, reported The Washington Post, which first reported the effort. The revelation, a day after it was reported that the US intelligence community believes Moscow is taking steps to help President Donald Trump win and at a time when Sanders is emerging as the Democratic front-runner, will only intensify the concern about Russia's role in the US presidential race.

Speaking to reporters in Bakersfield, California, Friday afternoon, Sanders confirmed that his campaign was briefed about the Kremlin's efforts about a month ago.

"It was not clear what role they're going to play. We were told that Russia, maybe other countries, are going to get involved in this campaign, and look, here's the message to Russia: stay out of American elections," Sanders said.

"And what they are doing, by the way, the ugly thing that they are doing, and I've seen some of their tweets and stuff, is they try to divide us up. That's what they did in 2016 and that is the ugliest thing they are doing -- is they are trying to cause chaos, they are trying to cause hatred in America. It's an ugly business and all of us have got to say, sorry, you're not going to do this in this election and again, as President of the United States, Mr. Putin, you will not interfere in our elections."

Asked at Wednesday night's debate about online aggression from some of his supporters, Sanders replied, "All of us remember 2016, and what we remember is efforts by Russians and others to try to interfere in our elections and divide us up. I'm not saying that's happening, but it would not shock me."

In 2016, a Russian government-linked troll operation sought to help Trump's candidacy and undercut that of Hillary Clinton, in part by posting messages in support of Sanders.

US intelligence officials have continued to consistently warn about Russia's ongoing efforts to interfere in American elections, noting threats to both the 2018 midterms and the 2020 presidential race.

On Thursday, CNN and other outlets reported that the intelligence community's top election security official delivered a briefing to lawmakers last week warning them that the intelligence community believes Russia is already taking steps to interfere in the 2020 election to help Trump.

The prospect of interference in 2020 will further test US defenses against foreign meddling, which Trump has repeatedly downplayed as he has dismissed any suggestion that Kremlin influence played a role in his election.

US intelligence officials, however, have continued to consistently warn about Russia's ongoing efforts to interfere in American elections, noting threats to both the 2018 midterms and the 2020 presidential race. Last month, FBI Director Christopher Wray told the Senate Judiciary Committee that Russia was continuing to "engage in malign foreign influence" online with the goal of sowing division and discord, "and to generate controversy, to generate distrust in our democratic institutions in our electoral process."

This story is breaking and will be updated.