WASHINGTON — Top national security officials vowed Thursday to defend American elections against what they called real threats from Russia only weeks after President Trump seemed to accept President Vladimir V. Putin’s denials of interference during a summit meeting in Finland.
After the meeting, Mr. Trump said he had not meant to endorse Mr. Putin’s denial of election meddling, but insisted that the culprit behind the intrusion“could be other people.” A few days later, he asserted that the idea of any meddling by Russia was “all a big hoax.”
But the men and women charged with detecting and defending against any threats to the American political process showed no such ambivalence. They bluntly said that Russia was behind a “pervasive” campaign to weaken America’s democracy and influence the 2018 election.
They also sought to reassure voters that federal, state and local governments were taking steps to guard against what Christopher A. Wray, the F.B.I. director, described as a “24-7 365-days-a-year” effort by Russia to sow division as Americans head to the polls in the fall.
“Russia attempted to interfere with the last election,” Mr. Wray told reporters in the White House briefing room, “and continues to engage in malign influence operations to this day. This is a threat we need to take extremely seriously and to tackle and respond to with fierce determination and focus.”
Dan Coats, the director of national intelligence, echoed that assessment, saying that “Russians are looking for every opportunity, regardless of party, regardless of whether or not it applies to the election, to continue their pervasive efforts to undermine our fundamental values.”
Mr. Wray and Mr. Coats were joined at the briefing by Kirstjen Nielsen, the secretary of homeland security, John R. Bolton, the president’s national security adviser, and Gen. Paul M. Nakasone, the head of the National Security Agency.
Officials at the briefing did not describe specific threats to the coming elections, and they were vague about how the government was responding to what they called Russia’s interference campaign. But they said Mr. Trump had directed them in a National Security Council meeting last week to aggressively confront the threats.
“Our democracy itself is in the cross hairs,” Ms. Nielsen told reporters. “The progress we have made is real, and the nation’s elections are more resilient today because of the work we are all doing. But we must continue to ensure that our democracy is protected.”
Ms. Nielsen said the government had “seen a willingness and a capability on the part of the Russians” to hack into the American election infrastructure, including voter rolls and voting machines. In addition to helping states and local governments prevent that hacking, she said her department was working to ensure that methods were available to validate the vote if a cyberattack occurred.
Senator Mark Warner, the top Democrat on the Senate Intelligence Committee, welcomed Thursday’s pledges of action from Trump administration officials, even as he chided the president for failing to take the lead in confronting Russian election-year aggression.
“Glad to see the White House finally do something about election security — even if it’s only a news conference,” Mr. Warner said on Twitter shortly after the briefing. “Now if only it was actually backed up by anything the President has said or done on Russia.”
Election experts say voting security has vastly improved since 2016, even if much remains to be done.
“All the states realize that securing their election systems — both administrative systems and voting machines — is a high priority,” said Charles Stewart III, a leading expert on election administration at the Massachusetts Institute of Technology. He said computer systems and voting machines were now probably the most secure part of the election infrastructure, thanks in part to a stepped-up effort by Homeland Security officials.
The greatest vulnerabilities, Mr. Stewart said, lie in individual political campaigns, few of which have come to terms with the threat posed by foreign actors like Russia. Barely a week ago, Senator Claire McCaskill, a Missouri Democrat, confirmed reports that Russian hackers had sought, apparently unsuccessfully, to break in to her computer network in the Senate, and at least one other campaign is known to have been attacked as well.
Despite Mr. Trump’s public comments playing down the threat from Russia, his security officials did not hesitate in directly blaming the Russian government as the primary culprit behind the interference campaign.
“We acknowledge the threat. It is real. It is continuing,” Mr. Coats said. “We are doing everything we can to have a legitimate election that everyone can have trust in.”
Mr. Bolton said the president did raise the issue of meddling with Mr. Putin at their meeting in Helsinki, and defended what he said had been Mr. Trump’s intense focus on the issue since he took office.
“I think the president has made it abundantly clear to everybody” in the government who oversees election security. Mr. Bolton said that Mr. Trump “cares deeply about it and that he expects them to do their jobs.”
The intelligence agencies do not believe that Russian efforts to interfere in the 2018 elections have reached the same level as in the 2016 presidential campaign, Mr. Wray said. But he said the government was braced for the possibility that Russia could ramp up its efforts overnight, requiring a more forceful response from the United States.
“Any moment is just a moment before the dial can be turned up,” Mr. Wray said.
In the meantime, Mr. Wray said that the Russian efforts to inject divisive misinformation into American social media were continuing daily, even when elections are not on the horizon.
Earlier this week, Facebook reported that it had identified a political influence campaign targeting the midterm elections and had removed 32 pages and fake accounts. Facebook did not link the campaign to Russia. The company has been criticized for not having done more to detect and remove the fake accounts created by Russians during the 2016 presidential campaign.
On Wednesday, Republicans in the Senate voted down an amendment to an appropriations bill that would have allotted $250 million to states to improve election security before the midterms. Only one Republican, Senator Bob Corker of Tennessee, voted for the measure. Others argued that Congress had already allotted $380 million for security improvements earlier in the year, and that more funds were not needed.
Experts on election administration took issue with that.
“There’s no finish line in election security,” said David J. Becker, the director of the Center for Election Innovation and Research, a Washington-based organization centered on improving voting technology and security. “There needs to be a consistent funding stream — probably in all critical areas, but particularly in elections — to secure those systems from attack.”
But Mr. Becker and others also said that states and localities needed to make quick and often cheap basic fixes to their systems, such as giving security training to workers and toughening passwords, and plan carefully before spending millions on new equipment.
Mr. Becker compared the state of election security to trying to prevent burglaries: The two best ways to stop burglars, he said, are to secure a house against break-ins and to deter burglars from even attempting them.
In election security, “We’re doing a pretty good job of protecting the house,” he said. “But where are the consequences against the criminal? That can only be done by the executive branch. The big question is, where is the president?”
Eileen Sullivan contributed reporting.
A version of this article appears in print on , on Page A16 of the New York edition with the headline: Russian Threat to Midterms ‘Is Real,’ Trump’s Top Security Officials Warn. Order Reprints | Today’s Paper | Subscribe