Ukrainian president Petro Poroshenko claimed "the fate of Europe" was being decided during a meeting with his Russian counterpart Vladimir Putin in Minsk.
Poroshenko insisted that his government would work on a ceasefire to bring the conflict in Eastern Ukraine to a halt, though it was unclear whether the separatist rebels would agree to a truce and how long it would take for it to be enforced.
The Ukrainian president described the meeting as "very though and complex", though he remained positive about the possibility of a truce.
"A roadmap will be prepared in order to achieve as soon as possible a ceasefire regime which absolutely must be bilateral in character," Poroshenko was quoted as saying by Reuters.
Putin said the first meeting between the two presidents since June had been positive, though he maintained Russia would not get involved in negotiations between Ukraine and the rebels currently occupying the eastern part of the country.
"We didn't substantively discuss that, and we, Russia, can't substantively discuss conditions of a ceasefire, of agreements between Kiev, Donetsk and Luhansk. That's not our business, it's up to Ukraine itself," Putin told reporters early on Wednesday.
"We can only contribute to create a situation of trust for a possible, and in my view, extremely necessary, negotiation process.
"We are ready to exchange opinions on the serious crisis situation in Ukraine and we are certain it cannot be solved by further escalation of force, without taking into account the real interests of the south-east of the country and peace talks with its representatives."
Ukraine wants to complete its "anti-terrorist operation" to regain control of the whole country, while Moscow has called for an immediate end to the hostilities in Eastern Ukraine, but with neither party seemingly willing to take a step back, the stalemate could drag on.
Belarusian President Alexander Lukashenko expressed doubts over the possibility of achieving a ceasefire, saying the parties remained distant.
"Their positions are different, sometimes completely different," he said.
On Tuesday, Ukrainian officials released video evidence of the interrogation of Russian soldiers, who had crossed the border between the two countries "by mistake" according to one of them.
"The Russians, who were detained together with their personal documents and weapons, have already testified," Andriy Lysenko, a spokesman for the Ukrainian army, said.
"According to the servicemen, their battalion was relocated by railway to Rostov region in Russia on 23 August, and around 3am on 24 August the department was given orders to march in a column consisting of several dozen armoured infantry vehicles.
"Only the officers were informed that the Russian servicemen would invade Ukrainian territory. A criminal case has been opened due to this invasion."