A Russian government think tank controlled by Vladimir Putin developed a plan to swing the 2016 US presidential election to Donald Trump and undermine voters’ faith in the American electoral system, three current and four former US officials have told Reuters.

They described two confidential documents from the think tank as providing the framework and rationale for what US intelligence agencies have concluded was an intensive effort by Russia to interfere with the 8 Nov election. US intelligence officials acquired the documents, which were prepared by the Moscow-based Russian Institute for Strategic Studies, after the election.

The institute is run by retired senior Russian foreign intelligence officials appointed by Putin’s office.

Hillary Clinton: Vladimir Putin helped 'influence' the election

The first Russian institute document was a strategy paper written last June that circulated at the highest levels of the Russian government but was not addressed to any specific individuals.

It recommended the Kremlin launch a propaganda campaign on social media and Russian state-backed global news outlets to encourage US voters to elect a president who would take a softer line toward Russia than the administration of then-President Barack Obama, the seven officials said.

A second institute document, drafted in October and distributed in the same way, warned that Democratic presidential candidate Hillary Clinton was likely to win the election. For that reason, it argued, it was better for Russia to end its pro-Trump propaganda and instead intensify its messaging about voter fraud to undermine the US electoral system’s legitimacy and damage Clinton’s reputation in an effort to undermine her presidency, the seven officials said.

The current and former US officials spoke on the condition of anonymity due to the Russian documents’ classified status. They declined to discuss how the United States obtained them. US intelligence agencies also declined to comment on them.

Putin has denied interfering in the US election. Putin’s spokesman and the Russian institute did not respond to requests for comment.

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The documents were central to the Obama administration's conclusion that Russia mounted a “fake news” campaign and launched cyber attacks against Democratic Party groups and Clinton's campaign, the current and former officials said.

“Putin had the objective in mind all along, and he asked the institute to draw him a road map,” said one of the sources, a former senior US intelligence official.

Trump has said Russia’s activities had no impact on the outcome of the race. Ongoing congressional and FBI investigations into Russian interference have so far produced no public evidence that Trump associates colluded with the Russian effort to change the outcome of the election.

Four of the officials said the approach outlined in the June strategy paper was a broadening of an effort the Putin administration launched in March 2016. That month the Kremlin instructed state-backed media outlets, including international platforms Russia Today and Sputnik news agency, to start producing positive reports on Trump’s quest for the US presidency, the officials said.

Russia Today did not respond to a request for comment. A spokesperson for Sputnik dismissed the assertions by the US officials that it participated in a Kremlin campaign as an “absolute pack of lies.” “And by the way, it's not the first pack of lies we're hearing from 'sources in US official circles',“ the spokesperson said in an email.

Russia Today and Sputnik published anti-Clinton stories while pro-Kremlin bloggers prepared a Twitter campaign calling into question the fairness of an anticipated Clinton victory, according to a report by US intelligence agencies on Russian interference in the election made public in January.

Russia Today’s most popular Clinton video - “How 100 per cent of the 2015 Clintons’ ‘charity’ went to ... themselves” - accumulated 9m views on social media, according to the January report.

The report said Russia Today and Sputnik “consistently cast president elect-Trump as the target of unfair coverage from traditional media outlets.“

The report said the agencies did not assess whether Moscow’s effort had swung the outcome of the race in Trump’s favour, because American intelligence agencies do not “analyse US political processes or US public opinion.”

Neither of the Russian institute documents mentioned the release of hacked Democratic Party emails to interfere with the US election, according to four of the officials. The officials said the hacking was a covert intelligence operation run separately out of the Kremlin.

The overt propaganda and covert hacking efforts reinforced each other, according to the officials. Both Russia Today and Sputnik heavily promoted the release of the hacked Democratic Party emails, which often contained embarrassing details.

Five of the US officials described the institute as the Kremlin’s in-house foreign policy think tank.

The institute’s director when the documents were written, Leonid Reshetnikov, rose to the rank of lieutenant general during a 33-year-career in Russia’s foreign intelligence service, according to the institute’s website. After Reshetnikov retired from the institute in January, Putin named as his replacement Mikhail Fradkov. The institute says he served as the director of Russia’s foreign intelligence service from 2007 to 2016.

Reuters was unable to determine if either man was directly involved in the drafting of the documents. Reshetnikov’s office referred questions to the Russian institute.

On its website, the Russian institute describes itself as providing “expert appraisals,” “recommendations,” and “analytical materials” to the Russian president’s office, cabinet, National Security Council, ministries and parliament.

On Jan. 31, the websites of Putin’s office and the institute posted a picture and transcript of Reshetnikov and his successor Fradkov meeting with Putin in the Kremlin. Putin thanked Reshetnikov for his service and told Fradkov he wanted the institute to provide objective information and analysis.

“We did our best for nearly eight years to implement your foreign policy concept,” Reshetnikov told Putin. “The policy of Russia and the policy of the President of Russia have been the cornerstone of our operation.”