Biden Warns Putin Of 'Severe Costs' Of Ukraine Invasion

President Biden warned President Putin that the US and allies would respond decisively if Russia invades Ukraine. This warning followed a phone call between the two leaders. The US has evacuated embassy staff from Ukraine and advised Americans to leave due to increased risk. Russia has stationed over 100,000 troops at the Ukraine border but denies planning an attack.

What does the text suggest about the risk and threat level regarding Russia's military presence?

How many troops has Russia amassed on its border with Ukraine?