They also said North Korea's nuclear program poses a potential "existential threat" to the United States, and that the time is nearing for Washington to respond to that danger.
In a Senate Intelligence Committee hearing on the most urgent threats facing the country, Coats and the heads of the CIA, FBI, NSA and two other spy agencies were unanimous in saying that Moscow's efforts to disrupt US politics are as intense now as they were in the 2016 presidential election.
"Throughout the entire community, we have not seen any evidence of any significant change" in Russian behavior, said Director of National Intelligence Dan Coats.
"There should be no doubt that Russia perceived its past efforts as successful and sees the 2018 US midterms elections as a potential target for Russian influence operations," he said.
"This is not going to change or stop," added National Security Agency Director Michael Rogers.
America's leading intelligence agencies concluded last year that Russian President Vladimir Putin had directed a broad intelligence effort to influence the 2016 presidential election to undermine the campaign of Democrat Hillary Clinton and boost Donald Trump's chances.
That effort included hacking and releasing emails and documents from the Clinton campaign, filling social media with posts and "news" items aimed at discrediting her, as well as targeting voter-registration operations and election databases.
Trump has repeatedly dismissed the idea that Moscow helped him -- and all allegations of collusion -- as "fake news," and criticized the intelligence agencies for repeating it.
But a large volume of information has surfaced on Russian use of social media to influence public opinion in US public policy debates.
"The Russians utilize this tool because it's relatively cheap, it's low risk, it offers what they perceive as plausible deniability, and it is proven to be effective at sowing division," Coats told the Senate panel.
"We expect Russia to continue using propaganda, social media, false-flag personas, sympathetic spokesmen, and other means of influence to try to build on its wide range of operations and exacerbate social and political fissures in the United States," he said.