The military force Russia has amassed along Ukraine's border could cause devastation in the event of an invasion, the chairman of the Joint Chiefs of Staff warned Friday.
Russian forces now include more than 100,000 troops consisting of air, naval, special forces, cyber and electronic warfare, command and control, logistics and engineering units, Gen. Mark Milley told reporters during a briefing at the Pentagon.
"If that was unleashed on Ukraine, it would be significant, very significant, and it would result in a significant amount of casualties," Milley said. "You can imagine what that might look like in dense urban areas, along roads and so on, so forth. It would be horrific; it would be terrible."
Read Next: Military Ordered to Overhaul Effort to Prevent Civilian Casualties After Botched Airstrikes
Milley and Defense Secretary Lloyd Austin held a press briefing Friday saying the U.S. stands ready to support NATO and respond to any attack on member nations, though Ukraine is not part of the alliance. Austin ordered 8,500 troops to be on heightened alert, but President Joe Biden has ruled out direct military action in Ukraine if Russian President Vladimir Putin orders an invasion.
“There is not going to be any American forces moving into Ukraine,” Biden told reporters on Tuesday.
Divisions also are forming among NATO allies over whether to call up the NATO Response Force, an elite coalition of 40,000 troops from member states that could include the 8,500 U.S. service members, according to the NATO secretary general.
"Although we don't believe that President Putin has made a final decision to use these forces against Ukraine, he clearly now has that capability," Austin said. "And there are multiple options available to him, including the seizure of cities and significant territories."
Austin said Putin may also attempt provocative political acts, such as recognizing breakaway territories within Ukraine as part of Russia, similar to what happened in Crimea in 2014.
"This is straight out of the Russian playbook. And they're not fooling us," he said.
Putin has demanded assurances that Ukraine will never join NATO and that the alliance will pull back from its eastern European flank. The U.S. has refused, and Secretary of State Antony Blinken sent a written response to Russia this week saying there could still be diplomatic dialogue if Putin stops the aggression.
For now, the military defense of Ukraine appears to be riding on its own forces, which may not be enough to repel a Russian invasion. Milley said the country has 150,000 active-duty troops, with many more in its reserves. Most are concentrated in the east along the Donbass region, where Kiev has been fighting a separatist war with Moscow-backed rebels.
"Their combat capabilities have improved since 2014 when Russia illegally annexed Crimea, but they need additional help to defend themselves, especially from an invasion force the size that Russia is currently massing," Milley said.
The U.S. has also given $2.7 billion in security assistance to Ukraine since 2014, including $650 million over the past year. That aid includes the Javelin, a portable missile capable of taking out Russian tanks, as well as other anti-armor weapons, artillery, grenade launchers and small arms, according to Austin.
The 8,500 U.S. troops put on heightened alert to deploy as part of a NATO Response Force to bolster eastern Europe are on hold stateside while the allies debate whether to greenlight their activation.
"That's a political decision," NATO Secretary General Jens Stoltenberg said Friday in a livestream event sponsored by the Atlantic Council. "There are some differences among the allies" on reaching a consensus to call up the 40,000 troops in the Response Force, including the 8,500 troops from the U.S.
The U.S. ready force includes members of the 82nd Airborne Division and 18th Airborne Corps at Fort Bragg, North Carolina, and troops with the 101st Airborne Division from Fort Campbell, Kentucky. The alert order also included units at bases in Arizona, Texas, Washington state, Louisiana, Georgia and Ohio.
Stoltenberg stressed that sending NATO forces into Ukraine itself in the event of a Russian invasion has been ruled out. "It is correct that there is not a plan to deploy NATO troops to Ukraine," he said.
He also confirmed that the Russian military buildup around Ukraine now includes the advanced S-400 air and missile defense system that Moscow has billed as an "F-35 killer."
Although activation of the NATO Response Force is being delayed, U.S. officials in recent days have spoken of unilateral workarounds by the U.S. to reinforce NATO members to deter Russia.
At a State Department briefing Thursday, Victoria Nuland, the assistant secretary of state for political affairs, suggested that U.S. forces already in Europe under U.S. European Command could shift to NATO's eastern flank to serve as a catalyst for activation of the NATO Response Force.
Nuland said that "sometimes it's the case that the U.S. can move more quickly and allies want that support and then NATO comes in, in support. So we're looking at all of those options and talking to all of the countries, particularly those on the eastern edge of NATO, a number of whom would like to see more support both from NATO and from the U.S."
At a Pentagon briefing Thursday, Defense Department spokesman John Kirby said that NATO Supreme Allied Commander Gen. Tod Wolters, wearing his second hat as head of European Command, is prepared to shift forces to the east.
"We're not taking off the table the possibility of using forces that are already in Europe," Kirby said. "It's entirely likely that some of that will be achieved through using organic capabilities that Gen. Wolters already has on the European continent."
-- Travis Tritten can be reached at firstname.lastname@example.org. Follow him on Twitter @Travis_Tritten.
Related: Troops at These Bases Are on Alert for Deployment over Ukraine Crisis