Ukrainian President Volodymyr Zelensky said situation in Donbas region remained extremely difficult reiterating that Russia was building up forces near the besieged city of Mariupol.
"There will be battles ahead. We still need to go down a very difficult path to get everything we want," he said.
US also said that Russia is refocusing its military efforts on the Donbas region which could herald a "longer, more prolonged conflict".
US President Joe Biden says that Russian counterpart Vladimir Putin may be "isolated" and could have placed some of his advisors under "house arrest".
NATO warned that it is not seeing a pull-back of Russian forces in Ukraine and expects "additional offensive actions".
Ukraine's government has sent 45 buses to evacuate civilians from the besieged city of Mariupol, where Russia has declared a local ceasefire following a global outcry over the suffering of civilians trapped by a month of relentless shelling.
