Xinhua file photos of Russian President Vladimir Putin (R) and Ukrainian President Volodymyr Zelensky.

Kazakhstan's former president Nursultan Nazarbayev is trying to arrange a meeting between Russian President Vladimir Putin and Ukraine's Volodymyr Zelensky, whose countries are at odds over the war between Kiev and pro-Russian separatists in eastern Ukraine.

"Zelensky has already agreed to a tete-a-tete, and [I have] informed the president of Russia about that. We shall see now [if Putin agrees]," Nazarbayev told a conference on international politics in the Kazakh capital Nur-Sultan on Tuesday.

Russia, however, gave a guarded response. Any such meeting must be well prepared and "meeting for the sake of meeting would serve little purpose," the Kremlin said.

Nazarbayev, who said he was ready to host such a meeting in Kazakhstan, spoke to Putin by telephone on Monday, his office said.

If the meeting took place, it would represent a breakthrough in ties strained for years by the conflict in eastern Ukraine.

Kremlin spokesperson Dmitry Peskov told reporters in Moscow on Tuesday, "Putin wants the reanimation of relations. But it is impossible to do that without reciprocity from Kiev.

"Clearly, Putin ... never refuses such meetings, but he believes that meeting for the sake of meeting serves little purpose, it must be well prepared."

The Kremlin said that its current focus was on a potential first summit in three years on the eastern Ukraine conflict between the leaders of France, Germany, Russia and Ukraine.

No date for that meeting has been confirmed.