Andrii Taran, speaking to the European Parliament's defense sub-committee in Brussels, also said he could not rule out that Russian forces in Crimea could "undertake substantive military provocations" in 2021.
He did not immediately provide evidence for his assertions.
In the past few weeks, Washington and its NATO allies have been alarmed by a large build-up of Russian troops near Ukraine and in Crimea, the peninsula that Moscow annexed from Ukraine in 2014.
"The hostility and unpredictability of America's actions force us in general to be prepared for the worst scenarios," Kremlin spokesman Dmitry Peskov told reporters last week.
Russia and Ukraine held simultaneous military drills on Wednesday as NATO foreign and defense ministers began emergency discussions on the massing of Russian troops near the Ukrainian border.