Speaking to a group of Russian journalists via video call, Zelensky said Russia's invasion had caused the destruction of Russian-speaking cities in Ukraine, and said the damage was worse than the Russian wars in Chechnya.

"Security guarantees and neutrality, non-nuclear status of our state. We are ready to go for it," he said, speaking in Russian.

But even as Turkey is set to host talks this week, Ukraine's head of military intelligence, Kyrylo Budanov, said Russian President Vladimir Putin was aiming to seize the eastern part of Ukraine.

"In fact, it is an attempt to create North and South Korea in Ukraine," he said, referring to the division of Korea after World War Two. Zelensky has urged the West to give Ukraine tanks, planes and missiles to help fend off Russian forces.

Zelensky later said in his nightly video address that he would insist on the "territorial integrity" of Ukraine in any talks.

In a call with Putin on Sunday, Turkish President Tayyip Erdogan agreed to hold talks this week in Istanbul and called for a ceasefire and better humanitarian conditions, his office said. Ukrainian and Russian negotiators confirmed that in-person talks would take place.

Top American officials sought on Sunday to clarify that the United States does not have a policy of regime change in Russia, after President Joe Biden said at the end of a speech in Poland on Saturday that Putin "cannot remain in power".

US Secretary of State Antony Blinken said Biden had simply meant Putin could not be "empowered to wage war" against Ukraine or anywhere else.

After more than four weeks of conflict, Russia has failed to seize any major Ukrainian city and signalled on Friday it was scaling back its ambitions to focus on securing the Donbass region, where Russian-backed separatists have been fighting the Ukrainian army for the past eight years.