A top Homeland Security Department official said Thursday his staff is "working around the clock" to prepare for America's enemies launching cyberattacks during the home stretch of the midterm elections.

Christopher Krebs, DHS undersecretary of the National Protection and Programs Directorate, said he was feeling "a little nervous" because the U.S. government wasn't yet aware of any effort to disrupt the midterms but his "paranoid disposition" meant he expected one.

For hackers, he said, 2018 was just the "warm-up" for the "big game" in 2020 when President Trump will be running to be re-elected to the White House for a second term.

Nearly two years after U.S. intelligence determined the Russians meddled in the last major election, Krebs delivered a speech in Washington, D.C., at a "CyberTalks" event and remarked on how little "activity" the feds, along with state and local governments, have seen with less than three weeks to go before the midterm elections.

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"We're not seeing activity right now, particularly anything close on the direct election hacking -- election infrastructure. We're not seeing anything right now along the lines of 2016 -- and that frankly makes me a little nervous," Krebs said.

"So if we're not seeing any activity and we're less than three weeks out -- what does that mean?" he continued. "I have a paranoid disposition anyway so I continue to work through what can we do. I don't want to have another failure of intelligence and I don't want to, most importantly, have another failure of imagination."

Krebs went on to give an outlook for the future.

"We are working aggressively right now with our partners in state and locals to work through what could an adversary do in the three weeks or two-and-a-half week leadup to the midterm elections," he said. Yes, the midterm is not the big game, the big game we think for the adversaries' probably 2020. '18's just the warm-up or the exhibition game. But nonetheless we're going to be ready, we've been working around the clock."

There have been efforts in Congress to boost election security spending. Democrats offered an amendment that would have given $250 million to states to fortify their election systems, but Senate Republicans blocked the measure during the summer.

Federal officials in the Trump administration have previously warned that future U.S. elections could be a top target for cyber-adversaries.

President Trump himself accused China in late September of 2018 midterm elections interference. That followed Director of National Intelligence Dan Coats saying, "what we see is ongoing capabilities and attempts" to influence U.S. politics, including from China, Russia, Iran, and North Korea.

[More: Obama knew about Russia election meddling, did nothing: Trump]

However, after Trump's comments, DHS Secretary Kirstjen Nielsen tamped down concerns, saying, "We currently have no indication that a foreign adversary intends to disrupt our election infrastructure."

Special counsel Robert Mueller has indicted a dozen Russian intelligence officials with allegedly hacking Democrats during the 2016 election as part his his larger Russian meddling investigation.

Trump signed an executive order in September creating a framework for imposing sanctions on foreigners who seek to influence U.S. elections.