US officials say President Barack Obama must carefully consider how to respond to what security experts believe was Russia's involvement in the hacking of Democratic Party organizations amid Washington’s concerns over a confrontation with Moscow.
US intelligence officials said publicly blaming the intelligence services of Russian President Vladimir Putin would bring immediate pressure on Washington to disclose its evidence, which relies on highly classified sources and methods.
The intelligence officials said they fear a rapid escalation of cyber attacks by Russia if Washington retaliates against Moscow in cyberspace.
Under a worst-case scenario, Russia's sophisticated hackers could attack financial systems, power grids and other critical infrastructure, the intelligence officials said.
Washington also has to manage diplomacy with Russia, including obtaining Moscow's help in ending the Syrian conflict, as well as managing Russia-NATO tensions over Ukraine and Eastern Europe.
"Despite how outrageous it is to interfere with a democratic election, the costs of coming out and saying the Russians did it would far outweigh the benefits, if there would be any benefits," said one intelligence official, speaking to Reuters on condition of anonymity to discuss a sensitive matter.
Russia has denied responsibility for hacking the emails of the Democratic National Committee (DNC) and a computer network used by Democratic presidential nominee Hillary Clinton's campaign.
Clinton suggested Sunday that Russian intelligence services had hacked into the DNC computers.
Last week, WikiLeaks released about 20,000 emails from the DNC that show top Democrats writing off Senator Bernie Sanders's chances during the primary presidential elections.
The FBI and other counter-intelligence agencies involved in the probe of the DNC hacking have not yet officially attributed the cyber attack to Russian government hackers.
But American security officials briefed on the investigation say evidence collected by the FBI so far points to groups that are known to US agencies for carrying out cyber attacks for the Russian government.
Generally, foreign spy agencies gather such information to try to better inform their governments about US politics. US spy agencies do the same in other countries.
Government and Democratic Party officials said they were unaware of any evidence that WikiLeaks had received the hacked materials directly from Russians or that WikiLeaks' release of the materials was in any way directed by Russians.