The leaders of Germany and France met Ukrainian president Petro Poroshenko in a hastily arranged mission to bring an end to the accelerated fighting in the east of the country.
The trip by German chancellor Angela Merkel and French president Francois Hollande will include a meeting with Russian president Vladimir Putin in Moscow today.
It came as concerns rose about whether the US would grant lethal aid to Ukraine and as Nato formed a quick-reaction force of 5,000 soldiers in response to Russia’s increased military muscle-flexing.
The meeting with Mr Poroshenko ended late last night and Mr Hollande and Ms Merkel left the presidential offices without comment.
Details of their peace plan remained unclear, although Mr Poroshenko said at the start of the meeting that it raised hopes for calling a quick ceasefire.
Foreign minister Pavlo Klimkin said the leaders discussed “steps so that the Minsk agreement can start working”.
That refers to a pact reached in September that called for a ceasefire, the pull-back of heavy weaponry by both sides, international monitoring of the Ukraine-Russia border and a degree of autonomy for the east.
The high-level diplomacy came as resurgent fighting killed eight more people in eastern Ukraine and fuelled fears the conflict is threatening Europe’s overall security.
More than 5,300 people have been killed since the fighting started in April.
The fighting in eastern Ukraine between Russia-backed separatist rebels and Ukrainian forces has intensified sharply over the past two weeks.
Russia vehemently denies it is providing equipment or troops for the insurgents, but US secretary of state John Kerry sharply rejected that claim.
“Let there be no doubt about who is blocking the prospects for peace here,” he said in Kiev, where he met Mr Poroshenko hours before the German and French leaders.
In Moscow, Mr Putin’s aide welcomed the new European initiative and said the Kremlin was ready for a constructive discussion.
Nato defence ministers in Brussels, however, boosted the alliance’s rapid response forces because of the fighting in Ukraine and Russia’s increased military muscle-flexing.
The senior Nato commander, US Air Force General Philip Breedlove, said that Russia continues to supply the separatists with heavy, state-of-the-art weapons, air defences and fighters.
Mr Kerry urged Russia to show its commitment to a peaceful, diplomatic solution to the conflict in eastern Ukraine by ceasing its military support for the separatists and bringing them to the negotiation table.
At a later news conference with Ukrainian prime minister Arseniy Yatsenyuk,Mr Kerry said President Obama “is reviewing all his options – among those options obviously is the possibility of providing defensive systems to Ukraine”.
At least three people were killed in overnight shelling in the rebel stronghold of Donetsk, local officials said, and Ukraine said five servicemen were killed and 29 others wounded in the last 24 hours.
France and Germany were hoping this time they can come up with a peace deal that both Ukraine and Russia can agree upon.
In a sign of the importance of the initiative, this will be Ms Merkel’s first trip to Moscow since Ukraine’s conflict broke out last year.
“It will not be said that France and Germany together have not tried everything, undertaken everything, to preserve the peace,” Mr Hollande said earlier.
In Moscow, Putin adviser Yuri Ushakov said Russia was “ready for a constructive conversation” aimed at stabilising the situation, establishing a dialogue between the Ukrainian government and the rebels and rebuilding economic ties between eastern Ukraine and Kiev.
Western diplomats said Mr Putin gave the French and Germans a nine-page peace plan, and that Mr Hollande and Ms Merkel were taking a repackaged version of that with them.
The diplomats said the European version drops the most objectionable elements of the Russian plan to fit what Ukraine and the Europeans want, such as some autonomy for eastern Ukraine with special protections for language, culture and local taxes.
Germany and other European nations remain fiercely opposed to sending arms to Ukraine. Federica Mogherini, the EU’s foreign policy chief, backed the French-German peace effort, saying: “There is no military solution to the crisis in Ukraine.”
European Union foreign ministers will be talking on Monday about increasing EU sanctions against Russia for its actions in Ukraine.
In Brussels, Nato Secretary-General Jens Stoltenberg said the group’s defence ministers boosted the size of the alliance’s response force from 13,000 to 30,000 in reaction to Russian actions in Ukraine and to Islamic extremism.
The alliance also moved to form a quick-reaction force of 5,000 ground troops.