The Ukrainian government says it won't agree a ceasefire deal with Russia that involves giving up territory.
Presidential adviser Mykhaylo Podolyak said Kyiv would not follow calls in the West for an urgent ceasefire that involved Russian forces remaining in territory they occupy in the south and east of the country.
He said making concessions would result in Moscow starting an even larger, more bloody offensive in the longer term.
His comments come as Russia continues its attempts to encircle Ukrainian forces defending the eastern city of Severodonetsk.
Russia occupied the Crimean Peninsula in 2014,and annexed it to its territory. It also took de facto control of parts of the Donbas region around the same time. Immediately before launching the invasion of Ukraine on 24 February of this year, Russian president Putin formally recognised the territories, which it calls the Lugansk and Donetsk People's Republics, as sovereign countries. After failing to occupy Kyiv and overthrow the Ukrainian government as part of its invasion plan, the Kremlin is now concentrating on expanding the territory under its control in the Donbas.
The internationally community recognises Crimea and the Donbas region as an integral part of Ukraine.
