(NBC NEWS) Determined to stop Russia’s interference in the presidential campaign, at least one of President Obama’s senior advisers urged him to make the ultimate threat to Russian President Vladimir Putin, U.S. officials told NBC News:

Mess with the vote and we will consider it an act of war.

But Obama opted not to issue a warning that specific when he spoke to Putin about the hacking during a September meeting at the G-20 summit in China, said intelligence officials offering NBC News exclusive new details.

Note: Read our discussion guidelines before commenting.