An adviser to President Zelensky's administration said Sunday that Russia was "trying to depopulate the east of Ukraine," amid heavy fighting there.
"I think the message they're sending is very clear," Tymofiy Mylovanov told CNN's Isa Soares in Lviv. "If you surrender, like Crimea in 2014, nothing is going to happen to you.
"If you resist, like Donbas, like the east of Ukraine, you'll be destroyed. (It) doesn’t matter if you're military or civilians. So the message Russia is sending is, 'surrender or be erased.'"
When asked about the hope Ukraine is still holding out for a visit by US President Joe Biden, Mylovanov said Biden should go to Kyiv since that would help demoralize Russian troops and further isolate Moscow.
Russia has revealed that the goal of its invasion is to take "full control" of southern Ukraine as well as the eastern Donbas region and to establish a land corridor connecting Russia to Crimea, the peninsula it annexed in 2014.
Ukraine has "repelled numerous Russian assaults along the line of contact in the Donbas this week," according to an intelligence update from the UK's Ministry of Defence Sunday.
Mylovanov, who is also president of the Kyiv School of Economics, said Ukraine needs long-range artillery from the U.S. to fight Russia.
He explained that "the terrain is different" in Donbas, so "the tactics of Russian forces (are) different." He added that financial assistance and military training is also needed.