Russian President Vladimir Putin has now "clearly" developed the capacity to attack Ukraine, the US military said on Friday while maintaining he has yet to make a final decision on a potential invasion of the former Soviet republic.
Joint Chiefs Chairman Mark Milley and Defense Secretary Lloyd Austin told reporters that the scope of Russia's military buildup is unprecedented in modern history, but separately maintained that conflict is not inevitable.
"We strongly encourage Russia to stand down and to pursue a resolution through diplomacy. Armed force should always be the last resort, success here is through dialogue," said Milley.
Still Putin's amassment of over 100,000 troops near Ukraine "gives him a number of options," said Austin, further maintaining "there’s no reason this situation has to devolve into conflict."
"What he’s done as he’s continued to move troops and resources into the region is increase his options," the defense chief said. "We won’t predict where his decisions will take him, but we remain concerned about the range of options he could pursue."
The US and its European allies have been warning for months that the mass buildup along Russia's border with Ukraine, and more recently in neighboring Belarus, could signal Russian intent to invade Ukraine. But Russia has steadfastly denied the charge, maintaining its forces are taking part in routine exercises.
But commenting on the sheer volume of Russian buildup, Milley said it is "larger in scale and scope in the massing of forces than anything we’ve seen in recent memory." Any comparison would have to date back to the Cold War, he added.
"Given the type of forces that are arrayed, the ground maneuver forces, the artillery, the ballistic missiles, the air forces, all of it packaged together, if it was unleashed on Ukraine it would be significant, very significant," the Joint Chiefs chairman said.
"It would result in a significant amount of casualties, and you can imagine what that would look like in dense urban areas, along roads, and so on and so forth. It would be horrific. It would be terrible. And it’s not necessary," he added.
Russia in 2014 annexed Ukraine's Crimean Peninsula in a move that has never been met with international recognition, and which has been decried by Ukraine and much of the global community as illegal. That year also saw Russia begin its support for separatist rebels in eastern Ukraine, a policy it has maintained for the past eight years.
In response to Russia's actions, NATO enhanced its presence in the eastern bloc, with four multinational battalion-size battlegroups deployed to Estonia, Latvia, Lithuania, and Poland on a rotational basis.
In addition to demanding NATO bar Ukraine from membership in the transatlantic alliance, Russian demanded the removal of those forces in Eastern Europe in order to remedy the ongoing crisis. NATO and the US rejected both requests, but left the door to diplomatic progress on other areas.
The US and European allies have been warning that Russia will face an unprecedented level and scope of economic sanctions, and Austin, the US defense chief, said that would be accompanied by the exact opposite of what Russia is seeking vis-a-vis NATO troops already stationed in Eastern Europe.
"As we've made clear, in addition to the significant economic and diplomatic costs that Russia will incur, a move on Ukraine will accomplish the very thing Russia says it does not want: a NATO Alliance strengthened and resolved on its western flank," he said.