Biden sends CIA Director to Moscow as fears grow over possible Russian invasion of Ukraine

According to anonymous American and Ukrainian sources, the visit involved direct talks with Russian security officials involved in the military build-up after satellite imagery and other intelligence noted 'irregular' movement of troops and equipment near Ukraine's northern border. After meeting with Russian security officials, Burns spoke to Ukrainian President Volodymyr Zelensky as part of an accelerating diplomatic effort to de-escalate tension between Moscow and Kiev.

Tensions have been high since the Russian invasion and annexation of Crimea in 2014, and have continued to simmer due to fighting between Ukraine and Russian separatists in the Donbas. Tensions escalated further over accusations from Kiev that Moscow 'purposely provoked' a deepening energy crisis in Ukraine, an advisor to Zelesnky saying that "the build [of troops], coupled with the energy blackmail, does suggest a more aggressive posture."

Asked Friday about the developing situation, Pentagon press secretary John Kirby noted that the 'scale' and 'size' of units that we're seeing [from Russia] is 'unusual', and that "[The United States] continues to monitor this closely... any escalatory or aggressive actions by Russia would be of great concern to the United States."

One anonymous US officials told CNN that the US has "serious concerns" about Russian build-up, adding "it would be foolish for us not to be considering an invasion or incursion."

Satellite images taken by Maxar Technologies on Monday demonstrate the kind of irregular Russian troop and equipment movements that US officials are worried about.

Asked about those satellite images, Kremlin spokesman Dmitry Peskov told reporters this week that "The movement of our military equipment or army units across the territory of the Russian Federation is exclusively our business." He added that "Russia has never threatened anyone, is not threatening, and does not pose a danger to anyone. But against the background of rather aggressive expansionist tendencies, especially on the part of NATO and other countries, Russia has always taken measures to ensure its security and will continue to do so."

Ukraine itself has downplayed notions of Russian military build-up near the border beyond 'normal' levels. Instead, the new Ukrainian Defense Minister Oleksiy Reznikov pointed to Russia having "established a practice of 'transferring and accumulating military units for the purpose of maintaining tension in the region and political pressure on neighboring countries".

Despite differing assessments in Washington, Burns also voiced American concerns about Russian use of gas exports for political leverage, as Ukraine and other European nations reliant on Russian natural gas are forecasted to face energy crises in the coming winter.

Concerns over the Kremlin's intentions have their current roots in Russia's invasion and annexation of the Crimean peninsula in 2014, and its invasion of Georgia in 2008. Putin has made clear his plans to keep Russian forces in Crimea despite international opposition and sanctions. Concerns in Washington, and in many European capitals are furthered by recent revisionist articles written by Putin and other senior Russian officials about the history of Ukraine and the foundation of the Ukranian state.