WASHINGTON, April 15 - Amid Russia’s massive troop buildup along its border with Ukraine, the top U.S. commander in Europe warned Thursday that NATO was prepared to respond to aggression, Defense News reported.

“We deter, and if deterrence fails, we’re prepared to respond to aggression with the full weight of the trans-Atlantic alliance,” Gen. Tod Wolters said during a House Armed Services Committee hearing on the region. Wolters is U.S. European Command’s chief and NATO’s supreme allied commander for Europe.

The comments came amid heightened tension between Washington and Moscow, which has more troops on the Ukraine border than at any time since 2014. Also this week, the Biden administration hit Russia with sanctions and diplomatic expulsions in response to its SolarWinds cyberattack and ongoing occupation of Crimea, which Russia seized and then annexed from Ukraine in March 2014.

“The president is taking hard and fast action with appropriately tailored responses to provide a clear signal of our resolve without escalation,” Laura Cooper, the Pentagon’s policy lead for Russia, told the panel.

The U.S. and its allies have sounded the alarm about the concentration of Russian troops along the border with Ukraine and increasing violations of a cease-fire in eastern Ukraine, where Russian-ba?ked separatists and Ukrainian forces have been locked in a conflict since the annexation.

Wolters said it is “of great concern, and our vigilance is high,” as a “very, very large” ground force had moved near Crimea and Donbass, with shifts in air and maritime forces as well. He added that Russia’s efforts to move supply lines forward had, however, “plateaued.”

Wolters assessed the chance of Russia invading Ukraine as “low to medium,” adding that the “likelihood would start to wane.” He declined to publicly share a more detailed assessment.

The comments came as Russian Defense Minister Sergei Shoigu said Tuesday that the country’s massive military buildup in the west was part of readiness drills amid what he described as threats from NATO. He said they would last for another two weeks.

In a hearing earlier in the week, Wolters affirmed that the Ukrainian military could repel a Russian offensive in the eastern part of the country “over time.” He said the U.S. continues efforts to train Ukrainian troops.

In the realm of security assistance, Cooper affirmed the Biden administration’s support for lethal aid to Ukraine and pointed to patrol boats and other equipment that were part of a $125 million package announced last month. (dn/ez)