World leaders are due to meet the president of Ukraine before starting the Nato summit in Wales.
After discussions with Russia's President Vladimir Putin, Ukraine's President Petro Poroshenko will update the US and EU leaders, reports BBC.
France has ramped up the pressure on Putin by axing its contract to deliver two navy assault ships to Russia.
The crisis in Ukraine is expected to be the main issue of the two-day Nato summit.
However, the rise of Islamic State, and Afghanistan leaders will also be discussed.
Poroshenko will brief UK PM David Cameron, US President Barack Obama and the leaders of France, Italy and Germany, in what correspondents say is a clear show of support to Ukraine's leader.
On Wednesday, President Poroshenko said he had agreed a "ceasefire process" during telephone talks with Putin.
Putin said he hoped a peace deal could be reached when rebels meet envoys from both states on Friday.
The ceasefire plan floated by Putin was "insincere", Nato chief Anders Fogh Rasmussen said in an interview with the BBC.
"I think the bottom line is that the Russians are not sincerely interested in a ceasefire. They continue to destabilize Eastern Ukraine," he said.
