The U.S. claims to have information indicating that Russia has "already prepositioned a group of operatives to conduct a false-flag operation in eastern Ukraine," laying the groundwork for a potential pretext to invade, according to a U.S. official.

Why it matters: Diplomatic talks between the U.S., its European allies and Russia failed to produce a breakthrough this week, raising fears that Moscow will invade Ukraine and unleash a devastating new war.

What they're saying: "The United States is concerned that the Russian Government is preparing for an invasion into Ukraine that may result in widespread human rights violations and war crimes should diplomacy fail to meet their objectives," the official said.

• "As part of its plans, Russia is laying the groundwork to have the option of fabricating a pretext for invasion, including through sabotage activities and information operations, by accusing Ukraine of preparing an imminent attack against Russian forces in eastern Ukraine."
• "The Russian military plans to begin these activities several weeks before a military invasion, which could begin between mid-January and mid-February. We saw this playbook in 2014 with Crimea."

The big picture: Russian diplomats insisted during talks in Geneva, Brussels and Vienna this week that they had no plans to invade, but repeatedly warned that a very dangerous situation would ensue if the U.S. and NATO refused to accept its security demands.

• Ukrainian military intelligence issued a similar warning about a potential "false flag" operation on Friday. Ukraine has also warned that an invasion would likely be preceded by an increase in cyber activity by Russian actors.
• Websites for the Ukrainian foreign ministry and other government agencies were knocked offline on Friday by a "massive cyberattack." The perpetrators have not yet been identified.
• The U.S. official said that "Russian influence actors" have already started to fabricate Ukrainian provocations on social media, including by "emphasizing narratives about deterioration of human rights in Ukraine and the increased militancy of Ukrainian leaders."

Go deeper: U.S. braces for Russian escalation as talks hit "dead end"