A Ukrainian delegation says it will hold face-to-face talks with Russian negotiators from Monday through Wednesday in Turkey. The Turkish government has acted as a mediator between the two sides.

But Russia's lead negotiator Vladimir Medinsky said the talks will take place on Tuesday and Wednesday.

The Ukrainian and Russian delegations had been holding online negotiations after meeting face-to-face in Belarus on March 7.

Attention is focusing on whether Russia and Ukraine will be able to achieve a breakthrough in these talks. But differences between them remain unresolved.

Analysts say Moscow is seeking a bargaining edge by gaining an upper hand in fighting in eastern Ukraine.

The Russian defense ministry recently said it would focus on liberating parts of eastern Ukraine. Pro-Russia armed militants hold sway over the regions.

The UK defense ministry said on Sunday that Russian forces appear to be concentrating on encircling Ukrainian forces directly facing the eastern separatist regions by advancing from Kharkiv in the north and Mariupol in the south.

The Institute for the Study of War, a US think-tank, said Russia's initial campaign aimed to seize the Ukrainian capital of Kyiv and other major cities "to force a change of government."

But the institute said Russia's announcement of its shift of focus to the east was "likely aimed mainly at a domestic Russian audience."