Russian President Vladimir Putin says Russia cannot agree to a ceasefire unless Ukraine agrees to take irreversible steps that are acceptable to Moscow.

Putin spoke to reporters on Thursday in Astana, Kazakhstan, after attending a summit of the Shanghai Cooperation Organisation.

Russia is stepping up its offensives on the frontlines in Ukraine. Asked about a possible ceasefire, Putin said Moscow cannot allow the enemy to use one to improve its position, arm itself or equip itself.

Putin stressed, "We need to ensure that the opposing side agrees to take steps that are irreversible and acceptable to the Russian Federation."

He added that a ceasefire is impossible without such agreement.

Last month, Putin said he would acquiesce to holding peace talks if Kyiv agrees to withdraw its troops and begins to do so from the four Ukrainian regions in eastern and southern Ukraine that Russia has unilaterally annexed in the conflict.

Ukraine has flatly rejected the idea.

Asked about strategic dialogue on nuclear disarmament with the US, Putin said constructive dialogue between Moscow and Washington is impossible during the heated US presidential election campaign. He added that Russia would wait for the election result in November.