That's just not true, Russia is short on tanks, Ukraine is reaching artillery parity, and Ukraine has a permenant manpower crisis whereas Russia has deep reserves it can pull from for training if given time. Western countries would stop aid flows to Ukraine during a ceasefire while Russia would be free to rearm. A temp. ceasefire would not help Ukraine.
Moreover, why would Ukraine want to negotiate a temp ceasefire? If they can snag security guarantees they have better odds of a long term peace.