American intelligence agencies have told the White House they now have “high confidence” that the Russian government was behind the theft of emails and documents from the Democratic National Committee, according to federal officials who have been briefed on the evidence. But intelligence officials have cautioned that they are uncertain whether the electronic break-in at the committee’s computer systems was intended as fairly routine cyberespionage — of the kind the United States also conducts around the world — or as part of an effort to manipulate the 2016 presidential election. The emails were released by WikiLeaks, whose founder, Julian Assange, has made it clear that he hoped to harm Hillary Clinton’s chances of winning the presidency. It is unclear how the documents made their way to the group. But a large sampling was published before the WikiLeaks release by several news organizations and someone who called himself “Guccifer 2.0,” who investigators now believe was an agent of the G.R.U., Russia’s military intelligence service.
The assessment by the intelligence community of Russian involvement in the D.N.C. hacking, which largely echoes the findings of private cybersecurity firms that have examined the electronic fingerprints left by the intruders, leaves President Obama and his national security aides with a difficult diplomatic and political decision: whether to publicly accuse the government of President Vladimir V. Putin of engineering the hacking.
Such a public accusation could result in a further deterioration of the already icy relationship between Washington and Moscow, at a moment when the administration is trying to reach an accord with Mr. Putin on a cease-fire in Syria and on other issues. It could also doom any effort to reach some kind of agreement about acceptable behavior in cyberspace, of the kind the United States has been discussing with China.
In an interview with Savannah Guthrie of NBC News on Tuesday, President Obama stopped short of accusing the Russian agencies from seeking to manipulate the election but said, “Anything’s possible.” He noted that “on a regular basis, they try to influence elections in Europe.”
Stealing information about another country’s political infighting is hardly new, and the United States has conducted covert collection from allies like Germany and adversaries like Russia for decades. Publishing the documents — what some have called “weaponizing” them — is a different issue. Mrs. Clinton’s campaign has suggested that Mr. Putin was trying to even the score after the former secretary of state denounced a 2011 Russian election as filled with fraud.