Sources in the Kremlin and close to Russian President Vladimir Putin have gone silent recently, US intelligence officials told The New York Times on Friday.

Officials don't believe the sources have been compromised or killed, but rather have become more afraid of getting caught and taken out as Moscow ups the ante in hunting down traitors.

This has left US intelligence agencies with no clear picture of Putin's intentions for interfering in the upcoming midterm elections.

For years, there has been a small but steady stream of intelligence leaks out of the Russian government, but US officials say information has all but dried up as the midterm elections approach, according to a new report The New York Times published on Friday.

US intelligence officials who spoke with the Times, on the condition of anonymity, said high-ranking Russian sources have gone quiet recently, leaving them with no clear picture of President Vladimir Putin's intentions for influencing the upcoming elections — which could lead the Democrats to taking back Congress.

It's never been a question of whether Russia will try interfere with the elections, but rather how and why. With the 2016 presidential election, the CIA and other US intelligence agencies knew well in advance that the Russians would try and influence the election to help Trump, former Director John Brennan testified last year. Russia President Vladimir Putin is pictured on Thursday. AP

The US is working with much less information now that sources high up in the Kremlin and close to Putin have stopped communicating.

US officials don't believe that the sources have been compromised or killed, but rather have become afraid of getting caught — especially after the high-profile poisoning of a former Russian intelligence officer in the UK, who traded secrets with MI6.

"The Russians are very focused and upset," CIA veteran John Sipher told the Times. "They have shown they are willing to kill sources."

Cultivating sources who are close to Putin is difficult, officials said, and in recent years there have only been a few speaking with the US.

While there are already signs of foreign interference — from the hacking of a Republican think tank to the creation of fake left-wing Facebook accounts — it's unclear whether Putin favors a specific US political party, undermine faith in democratic institutions or simply create chaos.

Some experts have asserted that Putin also seeks to target individuals and groups that have taken policy positions that disadvantage Russia.