Secretary of Defense Gen. Lloyd Austin argued that the threat of Russian invasion in Ukraine is important for maintaining international order as tensions reach a boiling point on the border. 

Russia has amassed nearly 150,000 troops along its southwest border and conducted military drills over the weekend. Russia continues to claim that it has no intention of invading neighboring Ukraine, but President Biden said Friday that he is confident that Russian President Vladimir Putin has decided to invade Ukraine. 

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Austin stressed on ABC’s "This Week" that the impact of any invasion will reverberate around the world, and Americans should care about the outcome.

"You’ve heard us talk all along about the importance of maintaining a rules-based international order," Austin said. "No one country should be able to dictate to another country what it can choose to do in terms of who aligns itself with or no one country should be able to redefine another country’s boundaries at-will." 

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Russia extended military drills near Ukraine's northern borders Sunday amid increased fears that two days of sustained shelling along the contact line between soldiers and Russa-backed separatists in eastern Ukraine could spark an invasion.

The exercises, originally set to end Sunday, brought a sizable contingent of Russian forces to neighboring Belarus, which borders Ukraine to the north. The presence of the Russian troops raised concern that they could be used to sweep down on the Ukrainian capital, Kyiv.

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Austin reiterated Biden’s pledge that U.S. troops stationed in the region are not there to engage in Ukraine’s defense and will not deploy into the country should Russia choose to take military action in Donbas or other regions of the country. 

He said he believes "our troops will be fine" in the event of a military invasion, but the civilian population of Ukraine will suffer enormously in his estimation. 

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"If [Putin] employs that kind of combat power, it will create enormous casualties for the civilian population," Austin said, noting that Russia has "assembled the right kinds of things you need to conduct a successful invasion." 

The Associated Press contributed to this report.