(NewsNation) — Former Defense Secretary Mark Esper suspects that the Kremlin drone incident was “locally launched.”

Ukraine and Russia pressed their wartime rhetoric Thursday, with Ukrainian President Volodymyr Zelenskyy expressing confidence that Vladimir Putin would be convicted of war crimes, and the Kremlin alleging that the U.S. was behind what it called an assassination attempt against the Russian president.

“I’m more inclined to think that it’s either a pro-Ukrainian group in Russia… Or it’s an anti-Putin group in Russia that did so,” Esper said during an appearance on “Elizabeth Vargas Reports.” “Given the nature or it, the proximity, and the fact that, in my perspective, it wasn’t intended to assassinate or do massive damage.”

The countries’ leaders have personally attacked each other multiple times during the war that Russia started by invading Ukraine in February 2022. The latest flare-up came Wednesday, with Russia’s claim that Ukraine had attacked the Kremlin in Moscow with drones meant to assassinate Putin.

“My suspicion is that this was intended to embarrass the Kremlin,” Esper added.

The Associated Press contributed to this report.