Russian forces are intensifying their shelling of areas in eastern Ukraine that are still under Ukrainian control.
Ukrainian officials in the east admit their defenses are outnumbered and outgunned.
Several officials said the United States is preparing to offer advanced long-range rocket systems that are now the main request of Ukrainian officials.
A larger package of US military assistance could be announced next week, they said.
Nine people were killed and 19 others wounded in Kharkiv on Thursday amid "heavy shelling" of residential areas, according to a Ukrainian military official.
In a new report, legal experts accuse Russia of inciting genocide and trying to "destroy" the Ukrainian people.
It comes as Ukraine's president said Russia's actions in eastern Ukraine reflect "an obvious policy of genocide."
