The foreign ministers of Russia, Ukraine, Germany and France gathered in Berlin after Moscow again denied claims it had sent weapons across the border to prop up the flagging separatist rebellion.
German Foreign Minister Frank-Walter Steinmeier said ahead of the talks that all sides must be "very careful... about sliding ever deeper into a direct confrontation between Ukrainian and Russian armed forces".
"This must be avoided at all cost," said Steinmeier before meeting Ukraine's Foreign Minister Pavlo Klimkin, Russia's Sergei Lavrov and Laurent Fabius of France.
The question would be "whether there is a path toward a ceasefire that is realistic and resilient and that offers us hope of ending the violence," he said.
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On the ground in east Ukraine, Kiev's military said it hoisted the national flag over a district police station in a northeast suburb of the second-largest rebel bastion of Lugansk after a fierce battle with pro-Russian separatists yesterday.
Ukraine also ramped up the stakes before the talks in Germany by alleging another military convoy that included three Grad rocket systems crossed over from Russia.
The fresh claims come as a furore still swirls over Kiev's earlier boasts that it destroyed part of a Russian armoured convoy which breached the frontier Thursday.
Ukraine's Klimkin said today's talks with his Russian counterpart would "not be easy" as Germany also demanded that Moscow clarify rebel claims that they had received hundreds of fighters trained in Russia to shore up their insurgency.
Meanwhile, Russia and Ukraine continued to haggle over a mammoth Russian aid convoy parked near the border as officials said inspections of the roughly 300 lorries would not start today.