Pentagon Press Secretary John Kirby on Sunday said that Russia appears to be "broadening its target set" following a series of airstrikes in western Ukraine that are creeping closer toward the Polish border, the beginning of NATO’s eastern flank.

Kirby appeared on ABC's "This Week" and addressed the latest Russian airstrike on a Ukrainian airbase located just 13 miles east of Ukraine’s border with Poland, a NATO member. Kirby said it was Russia’s third airstrike on military facilities and airfields in western Ukraine in the last couple of days.

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"We have been consistently concerned about NATO’s eastern flank and that airspace … and we continue to look for ways to bolster defense of NATO allies, we continue to look for ways to try to protect that airspace," Kirby said.

Pentagon Press Secretary John Kirby holds a news briefing at the Pentagon on March 09, 2022 in Arlington, Virginia. Kirby spoke on various topics including Russia’s invasion to Ukraine.

Pentagon Press Secretary John Kirby holds a news briefing at the Pentagon on March 09, 2022 in Arlington, Virginia. Kirby spoke on various topics including Russia’s invasion to Ukraine. ((Photo by Kevin Dietsch/Getty Images))

When asked about the concerns of Russia’s westward movement toward Poland, Kirby reiterated the administration's vow that the U.S. and its allies will protect NATO territory.

"We made it clear to Russia that NATO territory will be defended not just be the United States but by our allies," Kirby said.

The strike on the airbase in the Lviv Oblast is believed to be Moscow’s westernmost attack of the war. The attack killed at least 35 people and wounded 134, Reuters reported, citing regional governor Maksym Kozytskyy. 

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When asked whether a no-fly zone imposed in Ukraine would help deter such an attack, Kirby said that a no-fly zone "is combat" and would "lead to war with Russia."

"There is very little that you can see that would make sense for this war to be escalated between two nuclear powers," Kirby said.