Ukrainian President Petro Poroshenko has called on Russia to end its support for separatists in the east of his country, including withdrawing any Russian forces on Ukrainian soil.
Poroshenko also urged Russia to close the border between the two countries, saying doing so would lead to "peace and stability in Ukraine" within a matter of weeks.
Moscow denies playing any role in the conflict in eastern Ukraine.
Poroshenko was speaking on December 11 during a visit to Australia.
Speaking alongside Poroshenko in Melbourne was Australian Prime Minister Tony Abbott who expressed his country's "deep solidarity with the free country of Ukraine."
The two were speaking a day after fresh clashes between Ukrainian troops and separatists clouded prospects of a lasting cease-fire emerging from a "Day of Silence" in Ukraine as Kyiv ruled out peace talks until the rebels stop firing completely.
Australia and Ukraine have formed close ties since Malaysia Airlines Flight 17 was shot down in July over rebel-held territory in eastern Ukraine.
Of the nearly 300 people who died in the air disaster, 38 were Australian citizens or residents.
Kyiv and many in the West blame the separatists for shooting down the plane with a missile supplied by Moscow, something the Kremlin denies.
"If it turns out that people under Russian authority had a hand in this, we absolutely expect them to be surrendered to investigators and to prosecutors because this is an atrocity," Abbott said. "It was mass murder on a vast scale."
Poroshenko and Abbott also discussed a potential energy export deal, with the Ukrainian president saying his country may buy Australian uranium for its nuclear power stations, along with coal.
"Australia is an energy superpower and energy security is very important to Ukraine, particularly given its current vulnerability to supply shocks," Abbott said.
On December 10, Ukraine’s former President Leonid Kuchma -- Kyiv’s envoy in talks with Russia, separatists, and the Organization for Security and Cooperation in Europe (OSCE) -- said a new round of negotiations should not be held in Minsk in the coming days because separatists had violated a previously agreed cease-fire deal.
Kuchma was quoted by Interfax as saying, "In a situation where the second party is unable to ensure the cease-fire regime, I do not consider this meeting expedient."
He also reportedly said the separatists should "show that they really want peace and not war, and that they fully control their armed formations."
Denis Pushilin, the envoy for Donetsk separatists, told Interfax on December 10 that Kuchma’s remarks confirm Kyiv is not interested in obeying a September 5 Minsk peace accord and cease-fire deal.
That cease-fire deal has been broken on a daily basis, with more than 1,000 people being killed in eastern Ukraine since the accord was agreed upon in the presence of mediators from Russian and the OSCE.
