The leaders of Germany and France abruptly announced a summit with the Russian president, Vladimir Putin, in Moscow on Friday in response to overtures from the Kremlin, raising hopes of a breakthrough in the year-old Ukraine conflict.

The sudden and unusual decision by the chancellor, Angela Merkel, and the president, François Hollande, to travel to Moscow, with the French leader talking of decisions of war and peace, increased the stakes in the crisis while also raising suspicions that the Kremlin was seeking to split Europe and the US. Putin was said to have made “initiatives” to the European leaders in recent days.

Merkel and Hollande met the Ukrainian president, Petro Poroshenko, in Kiev on Thursday evening but left without making any comment. Ukraine’s foreign minister, Pavlo Klimkin, said on Twitter that the leaders had discussed “steps so that the Minsk agreement can start working”. A ceasefire signed in Minsk in September froze the frontlines at their positions at the time, but never held.

Friday’s visit will be Merkel’s first trip to Russia since the outbreak of violence in eastern Ukraine, which has now cost more than 5,000 lives. The increase in diplomatic efforts came as the US secretary of state, John Kerry, also met Poroshenko and other top officials in Kiev.

At a joint news conference with Ukraine’s prime minister, Arseniy Yatsenyuk, Kerry sounded lukewarm about Merkel and Hollande’s visit. He said Putin had sent “a couple of ideas” to France and Germany, and the pair had come up with a counter-proposal, but he did not give details. Kerry also said the US wanted a diplomatic solution but was reviewing all options including “the possibility of providing defensive systems to Ukraine”.

EU diplomats and officials said that growing US talk of arming Ukraine was pushing the Russians and Europeans towards a diplomatic deal, with both sides keen to avoid weapons deliveries but also to keep the US on the sidelines of the diplomacy.

Yatsenyuk, uneasy at the idea of a deal being cut in Moscow without Ukraine at the table, said Putin wanted “to split the unity between the EU and the US”. He said negotiations should take place between all parties, including Ukraine and the US. Kerry will not travel to Moscow with Merkel and Hollande.

“The best way to save this conflict is to retain unity of the free world. The EU, the US and Ukraine. We stay together, we act in concert,” said Yatsenyuk.

As fierce fighting continues, diplomatic negotiations are entering a key period, with Merkel due to travel to Washington early next week, after her Kiev and Moscow trips, to meet Barack Obama.

A number of US officials have signalled recently that Washington may be open to providing Ukraine with direct military aid. Kerry said the US president would make a decision on providing defensive weapons to Ukraine soon. Merkel has ruled out sending weapons, and her trip to Moscow could be a last-ditch attempt to avoid Washington arming Ukraine and the prospect of a proxy war between the US and Russia in Ukraine.

The aftermath of shelling in a residential area of Donetsk on Wednesday, as fighting between Ukraine’s armed forces and pro-Russian separatists intensifies. Guardian

In Washington German diplomats are anxious to counter mounting US pressure to arm Ukraine. They stress that Merkel would not be going to Moscow if she did not believe Putin was now ready to make a deal.

“There is something in her hands,” ambassador Peter Wittig said. “She is not going empty handed.”

Intensive preparations for a summit with Putin in Kazakhstan fell through last month because Merkel concluded it would be a waste of time.

Putin’s spokesman, Dmitry Peskov, said Merkel, Hollande and Putin would discuss ways to end the “civil war” in Ukraine – a continuation of the Kremlin line that Russia is not a party to the conflict.

Putin held an urgent session of Russia’s security council to discuss the situation in eastern Ukraine before the upcoming meeting, Peskov said. Presidential aide Yury Ushakov said he hoped Hollande and Merkel’s plan was “comprehensive and takes into account the many suggestions made by our president”. He said the stimulus for the meeting had come from a comment Putin made during a phone conversation that the leaders of France and Germany “are always welcome guests in Moscow”.

Russia has repeatedly made blanket denials of any involvement in the conflict, despite evidence of logistical and military support to the rebels.

President Poroshenko presents an award to a wounded serviceman during his visit to a military hospital in Kharkiv. Photograph: Mykola Lazarenko/AFP/Getty Images

In Kiev there is a growing sense that the rebel-held areas of the east may be lost for some time, and privately many in the political establishment express a willingness to accept a “frozen conflict”, in which Moscow would have to fund the rebel territories it has helped create.

Moscow, however, apparently wants Kiev to pay for the territories while having no control.A foreign minister of an EU country told the Guardian that the Minsk agreements might only form a starting point for a new peace deal, while senior EU officials said that the recent Russian-backed separatist offensive in eastern Ukraine was aimed at creating new facts on the ground and a new ceasefire line before a peace process was initiated.

“Minsk is a table where Russia has to play its role. The beginning of the path is there,” said the minister. “There are big discussions on changing the Minsk protocols.”

Putin did not want to annex the rebel-held parts of eastern Ukraine, but keep control of them in order to weaken and destabilise Ukraine well into the future, the minister said.

“This is about changing the ceasefire line and about changing the conditions [for negotiations],” said a senior EU official.

Putin’s proposals include a demand for autonomy for the pro-Russian separatist-held regions of Donetsk and Luhansk in eastern Ukraine, but also insistence that the Ukrainian government maintain budget payments for social and public services in the breakaway regions. Kiev – officials in Brussels said – is certain to reject this because it is tantamount to asking the Ukrainian government to fund the partition of its country.

But in addition to such demands, Putin is also said to be offering sweeteners.

In Moscow, the foreign ministry spokesman Alexander Lukashevich said the three leaders would discuss the deployment of UN peacekeepers to eastern Ukraine.

Diplomats said the Russian offer had to be substantive otherwise Merkel would not have agreed to travel to Moscow. As the west’s key mediator on Ukraine, Merkel has spoken to Putin more than 40 times in the past year, but Friday will be the first time in the crisis that she has gone to Moscow.

She last saw Putin, for four hours of tete-a-tete talks, in Brisbane in November following which she delivered, in Sydney, her fiercest critique yet of the Russian leader.

While Russia has publicly said it wants a peaceful resolution to the conflict and blames Kiev for escalating violence, a separatist push on the ground has been accompanied by signs that Russia could be about to up its direct military involvement again, despite its claims it is not party to the conflict.

This week, soldiers’ rights advocates in Russia said they had noticed an uptick in appeals from conscripts being pressured to sign a contract and deploy to the border region of Rostov, a tactic that has reportedly been used to send troops into eastern Ukraine. On Thursday, Putin signed an order to call up Russia’s military reserves for training exercises.

When asked about Russian denials of their involvement in eastern Ukraine, Yatsenyuk was scathing: “If they need, I can give them my glasses,” he said.

Nato met on Thursday to flesh out details of a rapid reaction force of about 5,000 troops to be deployed in eastern Europe. Britain’s Ministry of Defence confirmed that the UK would contribute as many as 1,000 troops to the force and would deploy four RAF Typhoon jets to police the air space above the Baltic states.