Ukraine has requested an urgent meeting with Russia and dozens of other European states to explain Moscow's buildup of forces along the ex-Soviet state's frontier.
Foreign Minister Dmytro Kuleba wrote on Facebook late Sunday that Russia had ignored Kyiv's formal request for an explanation about why Moscow had positioned more than 100,000 troops and advanced weapons around Ukraine.
"Ukraine is convening a meeting with Russia and all member states in the next 48 hours to discuss the reinforcement and movement of Russian forces along our border," he wrote.
Read More: Ukraine says European push helping avert war
The 1990 Vienna Document requires the 57 members of the Organization for Security and Co-operation in Europe (OSCE) to share information about their military forces and notify each other about major activities.
There was no immediate response from Moscow to Kuleba's request.
The United States fears that Russia's buildup of forces could lead to an invasion of Ukraine "any day".