Russia is amassing troops near the Ukrainian border: What you need to know

Russia has built up roughly 100,000 troops near its border with Ukraine, prompting fears of an attack in early 2022. U.S. intelligence is warning that Russia could invade Ukraine as early as January, a U.S. official confirmed to CBS News last week. 

It's not yet clear if Russia actually plans to invade — but the buildup of forces has sparked international concern. At a virtual summit on Tuesday with Russian President Vladimir Putin, President Biden reiterated the U.S.' commitment to Ukrainian independence and threatened severe economic sanctions if Russia invades. 

Here's what you need to know about the conflict.