The U.S. military will conduct joint exercises with Ukrainian forces in the spring, said Lt. Gen. Frederick Hodges, commander of U.S. Army Europe, who was part of a U.S. military delegation visiting Kiev this week. Ukrainian servicemen will be trained to set up communications posts and defend against Russian artillery, among other tasks.

The Wednesday announcement comes amid claims from NATO Secretary-General Jens Stoltenberg that Russia has increased the number of heavy arms it is sending into eastern Ukraine, while Kiev also accused the Kremlin of deploying 9,000 troops to the insurgency.

"For several months, we have seen the presence of Russian forces in eastern Ukraine,” said Stoltenberg, a former Norwegian prime minister. “And we also see a substantial increase in the number of Russian heavy equipment there. And we speak about equipment like tanks, artillery, armored vehicles, advanced air defense systems, and this Russian military presence with forces and equipment in eastern Ukraine does not contribute to a peaceful and negotiated solution.”

The U.S. has downsized its presence in Europe and withdrawn from military bases across the continent over the last 25 years, but increased hostility from Russia toward the West and Ukraine has prompted the Pentagon to send troops and equipment to the Baltic states, Poland and other front-line eastern allies to take part in training exercises. However, U.S. officials have not yet proposed permanent deployments to any of those locations.

The U.S. Army commander in Europe's trip to Ukraine coincides with increased fighting at Donetsk airport, where it’s alleged that regular Russian forces are fighting alongside pro-Russian rebels to gain control. Multiple media reports on Wednesday suggested that separatists had completely destroyed the airport and driven the Ukrainian military out.