German Chancellor Angela Merkel voiced alarm Thursday at the fraying ceasefire in Ukraine, but said she was "cautiously optimistic" a deal would be struck to renew Russian gas supplies to Ukraine. She spoke after talks with visiting Polish Prime Minister Ewa Kopacz. Both their countries partly rely for winter heating on gas pipelines which cross Ukrainian territory and worry that Russia's cut-off since June in gas supplies to Ukraine may escalate into a regional crisis. Guenther Oettinger, the EU energy commissioner, proposed the same day that Russia, Ukraine and the EU meet October 21 in Berlin to discuss terms for Russia to resume gas supplies to Ukraine, Brussels officials said. A previous meeting failed to achieve a breakthrough, despite an EU offer to guarantee 3.1 billion dollars in payments by Kiev. "I hope Commissioner Oettinger will succeed after all in finding a solution that provides us and Ukraine with security of supply over the next few months," said Merkel. "Intense work is going on on this, and, because of that, I am cautiously optimistic." The chancellor said it was "obvious" that the Ukraine ceasefire accord reached last month in Minsk was not being applied. "Both us want as many observers as possible in Ukraine," she said, referring to lagging efforts to send in military observers under the aegis of the Organization for Security and Co-operation in Europe (OSCE). These could become "an element of better monitoring." "The precondition for this is that the ceasefire really holds, and if the United Nations says yesterday that more than 300 people have lost their lives since this truce went into force, then you see how fragile the situation still is." Kopacz, who was making her first visit to Berlin since assuming the premiership, admitted "difficult" differences remained with Germany about reducing emissions of climate-changing gases. Poland, which relies heavily on coal to fire power stations, has been dismayed at EU plans to force steep reductions in carbon dioxide emissions, charging these would lead to higher electricity prices. Kopacz said more talks in Berlin between their staff on the issue were planned before next month's EU summit. "The solution will arrive at the (European) summit, not here in Berlin," she added. The premier, who was scheduled to continue to Paris after her Berlin meeting, added that Poland was looking at giving up its zloty currency and joining the eurozone, but two conditions needed to be satisfied. "Poland's economy and its public finances must be in the right condition," she said. "And the eurozone must be really safe and free of crisis." Merkel said Germany was "open" to Poland using the euro, noting Berlin had welcomed Estonia and Latvia when they joined the currency union. The new premier replaces Donald Tusk, who has resigned to become president of the European Council. Merkel said she and Kopacz had made a good start in their relationship. "The chemistry between us is fine. You can see that the two of us are very relaxed (with one another)," she told reporter.