Ukrainian President Petro Poroshenko signaled on Friday he would seek a pullout of all Russian forces from Ukraine and re-establishment of Ukrainian control of the joint border when he meets Russian, German and French leaders next month.
Poroshenko, who meets Russian President Vladimir Putin and the two other leaders in Paris on Oct. 2, has come under fire at home from some political allies for appearing to concede too much to pro-Russian separatists under a peace agreement brokered by the four powers in Minsk, Belarus.
He and his government were shaken by nationalist-led riots outside parliament on Aug. 31 after deputies voted in favor of giving greater autonomy to rebel-held areas. Three Ukrainian guardsmen were killed and scores of others were wounded when a grenade was thrown from the crowd.
Violence in eastern Ukraine, where government forces and separatists confront each other, has mostly subsided since Sept. 1 under a cease-fire agreed in Minsk.
But a Kiev military spokesman said on Thursday that an estimated 30,000 Russian troops and 10,000 separatist fighters remained in the eastern Donbass region. Moscow denies that its troops are engaged there.
Speaking to an international audience in Kiev on Friday, Poroshenko said Ukraine was concerned that OSCE monitors were being denied access to sensitive areas on the joint border between Russia and Ukraine where they could track troop pullouts and the withdrawal of heavy weapons from front lines.
"A full withdrawal of all occupation forces from Ukrainian territory and closing the Ukrainian-Russian border: these are the two main preconditions for peace and stability in the Donbass," Poroshenko said.
"We don't have any civil war. We don't have any internal conflict. It is very simple. We have aggression against Ukraine and occupation of independent Ukraine. It's absolutely clear that the aggressor is Russia," he said.
The separatist rebellion erupted in April 2014 after Russia annexed Crimea in response to the toppling of a pro-Moscow president in Kiev by street protests, and the succession of a Western-oriented leadership under Poroshenko.
About 8,000 people are estimated to have been killed and several thousands wounded in the conflict, according to UN Human Rights Office figures.