Ukrainian President Petro Poroshenko has said he would ask Russian counterpart Vladimir Putin to withdraw pro-Moscow militants from Ukrainian territory.
Poroshenko and Putin are set to meet during a summit of the Russia-led Customs Union in Belarus next week, which will also be attended by senior EU officials.
Poroshenko was quoted by his website as saying that the Ukrainian side "would call for the [rebel] fighters to be withdrawn from Ukraine." He said, "I am sure we will succeed in this."
The statement was published as the first truck in what Russia says is a humanitarian aid convoy was poised to cross into eastern Ukraine after days of delays.
A convoy of more than 250 trucks has been halted near the border amid Ukrainian concerns it could be used to supply pro-Russian rebel fighters who oppose Ukrainian rule.
International Committee of the Red Cross (ICRC) head of operations for Europe and Central Asia Laurent Corbaz told a news conference in Moscow on August 21 that "the convoy could start its operations -- hopefully tomorrow."
Moscow says the trucks are carrying aid for civilians in the Donetsk and Luhansk regions, where the United Nations says more than 2,000 people have been killed in months of fighting.
When the Russian truck convoy left the Moscow region on August 12 and headed for the Ukrainian border, it deepened concerns in Kyiv about intervention by Russia.
Kyiv has demanded security guarantees from all sides including the rebels before allowing the convoy into Ukraine, where it is to distribute aid under the aegis of the ICRC.
Meanwhile, Ukrainian military spokesman Andriy Lysenko said three refugees, including a 5-year-old child, were killed on August 21 when rebel gunfire hit their car near Luhansk, a separatist stronghold that is without water or regular power supplies.
Lysenko said five Ukrainian servicemen were also killed overnight.
Authorities in the city of Donetsk -- the rebels' main stronghold -- said at least two civilians were killed by artillery fire and prison officials said four inmates in the nearby city of Makyivka were killed when a shell hit their prison.
Lysenko said government troops were still fighting separatists in and around Ilovaysk, a town near Donetsk where fighting raged earlier this week, even though he said Ilovaysk was under government control.
Ukraine and the West have accused Moscow of orchestrating the rebellion and equipping the rebels with weaponry.
Ukraine's military said on August 21 that its forces near Luhansk had captured two Russian armored vehicles with documents linking them to an elite Russian paratrooper unit that had earlier been linked to the seizure of Crimea.
Russia rejected allegations that it had sent vehicles into Ukraine.