The leaders of the United States and leading European Union countries will discuss Russia's actions in Ukraine at a meeting with President Petro Poroshenko on the sidelines of the NATO summit in Wales, a British government source said.
"The Alliance must demonstrate clearly that Russia's actions are unacceptable and that we stand by the people of Ukraine and their right to decide the future of their country," the source said on condition of anonymity.
Prime Minister David Cameron will join U.S. President Barack Obama, German Chancellor Angela Merkel, French President Francois Hollande and Prime Minister Matteo Renzi to discuss the situation in Ukraine.
"The meeting will provide leaders with the opportunity to hear President Poroshenko's assessment of the latest situation on the ground and his discussions with President (Vladimir) Putin," the source said. "It will also send a clear signal of their support for Ukraine's sovereignty and that the onus is on Russia to deescalate the situation."
Poroshenko spoke by telephone with Putin earlier on Wednesday and his office said they had agreed on a cease-fire. Russia, which says it is not involved in the fighting, denied it had made such an agreement and Putin later outlined his own plan for a cease-fire, which Ukraine's prime minister dismissed.
