By Andrea Shalal
MUNICH (Reuters) - Moscow's efforts to meddle in Western elections are backfiring, serving instead to strengthen and unify a broad range of people against Russia, top U.S. security official H.R. McMaster said on Saturday, a day after Washington indicted 13 Russian individuals and three Russian companies.
Russian officials denied the allegations, and one senior diplomat dismissed the charges as "fantasies" being used by some in Washington for political gain in a deeply divided United States after the election of Donald Trump as president.
Officials from both countries sparred openly about everything from espionage to nuclear weapons at various events at the annual Munich Security Conference, attended by some 500 high-level diplomats, executives and politicians.
McMaster, the U.S. National Security Adviser, told the conference the surprise FBI indictments provided "incontrovertible" evidence of Russia's actions.
The indictments and the continuing U.S. investigation could potentially convince Moscow to back off, he said, noting that U.S. officials were also becoming more adept at "tracing the origins of this espionage and subversion".
"Russia may evaluate what it's been doing ... because it's just not working," he said.
The U.S. indictments on Friday said a Russian propaganda arm oversaw a criminal and espionage conspiracy to interfere in the 2016 U.S. presidential campaign to support Donald Trump and disparage his rival, Hillary Clinton.
It said Russians adopted false online personas to push divisive messages; traveled to the United States to collect intelligence, visiting 10 states; and staged political rallies while posing as Americans to "sow discord in the U.S. political system, including the 2016 U.S. presidential election".
Russian Foreign Ministry spokeswoman Maria Zakharova denounced the allegations as "absurd" and ridiculed the notion that so few Russian nationals could undermine U.S. democracy.
Russian Foreign Minister Sergei Lavrov also pushed back, saying he viewed the allegations as "just blather".
In a subsequent panel at the conference, Sergei Kislyak, who served as Russian ambassador to Washington at the time of the alleged election meddling, denied that he or his staff had carried out any such activities during his time there.
"When it comes to my being ambassador in the United States, we never got involved in the political life in the United States. I have never done anything of this sort, none in my embassy did," he said.
"Whatever allegations are being mounted against us are simply fantasies that are being used for political reasons inside the United States," he said.
Kislyak, whose contacts with members of Donald Trump's campaign team made him a central figure in the row about any Russian influence over the U.S. presidential election, left Washington in August.
McMaster said Russia was trying to polarize Western societies by backing "the most extreme forms of fascist groups" and left-wing groups, but the result had been to strengthen and unite people in the political middle against Russia.
He noted that the deeply partisan and divided U.S. Senate had voted 98 to two to renew sanctions against Russia, calling the vote clear evidence that Moscow's campaign was not working.
Senior officials from the two countries also traded barbs over a new U.S. nuclear arms policy that will expand the Americans' low-yield nuclear capability.
"The American administration seems to be taking a very relaxed position as to the conditions of the use and the first use of nuclear weapons," said Kislyak.
"They are looking at nuclear weapons more like a war fighting instrument, rather than a classical deterrent."
John Sullivan, Deputy U.S. Secretary of State, said: "Our nuclear posture review is based on a factual assessment of the changed security circumstances ... We want to deter nuclear war. We don't want to engage in nuclear war."
Despite the heated exchange, the two men shook hands warmly at the end of the panel discussion.
(Additional reporting by Paul Carrel in Berlin and Joern Poltz; Editing by Andrew Bolton)