Russian President Vladimir Putin has met Ukrainian President-elect Petro Poroshenko for the first time since his election, at a D-Dayevent in France.
German Chancellor Angela Merkel, who was also present, told Mr Putin earlier that Moscow bore "great responsibility" for making peace in Ukraine.
She said that with Mr Poroshenko's election, it was time for stability.
Mr Putin denies military involvement despite the presence of Russian fighters among the rebels.
Germany is cautious about expanding sanctions against Russia.
Mrs Merkel told a summit of the G7 states in Brussels this week that further sanctions would take effect only if there had been "no progress whatsoever".
Targeted sanctions were introduced by the EU and US after Russia annexed the Ukrainian territory of Crimea in March, following a controversial referendum on joining Russia.
Since then, a bloody insurgency has gripped Ukraine's eastern provinces of Donetsk and Luhansk, on the Russian border.
Pro-Russian separatists there have declared independence from Ukraine, refusing to recognise the pro-EU government which replaced President Viktor Yanukovych after he was ousted in February.