Russian President Vladimir Putin said on Friday that Russia and Ukraine's demands for peace were "absolutely contradictory", after two rounds of peace talks had failed to bring the sides closer to an elusive ceasefire.

Russian and Ukrainian negotiators swapped memoranda outlining their visions for how to end the three-year conflict at peace talks in Istanbul this month.

But other than large-scale prisoner exchanges, the talks have failed to result in any progress toward ending the fighting, triggered by Russia launching its military offensive in February 2022.

"As for the memorandums, as expected, nothing surprising happened... these are two absolutely contradictory memorandums," Putin said at a press conference in Belarus.

At talks, Russia has demanded Ukraine cede even more land and give up Western military support as a precondition to peace -- terms Kyiv says are unacceptable.

Putin has repeatedly rejected calls for an immediate ceasefire and has escalated his aerial attacks as his army advances across the battlefield.

He also said Russia was looking to cut its military expenditure from next year.

"Next year and the year after, over the next three-year period, we are planning for this," Putin said.

"6.3 percent of Russia's GDP goes on defence needs. That is 13.5 trillion rubles (US$172 billion). It's a lot," Putin said, acknowledging it had the potential to create headaches for the government budget. (AFP)