The U.S. failure to retaliate strongly for the 2014 cyber attack against Sony Pictures may have helped inspire Russian hackers who sought to interfere in the 2016 U.S. election, a senior congressional Democrat said on Tuesday.

"Russia may have concluded that they could hack American institutions and there'd be no price to pay," Representative Adam Schiff, the top Democrat on the House of Representatives Intelligence Committee, told a news breakfast sponsored by the Christian Science Monitor.

Schiff suggested that Washington team up with European allies to impose sanctions that would hit the Russian economy.