US Secretary of State Rex Tillerson on Thursday accused Russia of instigating unrest in eastern Ukraine, where violations against an agreed ceasefire have increased in recent weeks.
Tillerson's comments came during a speech on the first day of a Ministerial Council of the Organization for the Security and Co-operation in Europe (OSCE) in the Austrian capital, Efe news reported.
"We should be clear about the source of this violence," said the top US diplomat. "Russia is arming, leading, training and fighting alongside anti-government forces in Ukraine."
Tillerson was expected to hold a bilateral meeting with his Russian counterpart Sergei Lavrov later in the day.
He pointed out that more civilians had died in the conflict in 2017 than last year and that ceasefire violations in Donetsk and Luhansk had risen by 60 per cent.
In a speech delivered shortly before Tillseron's, Lavrov had denounced what he said was the reckless expansion of NATO in Eastern Europe and the deployment of US anti-aircraft missile systems in Europe.
The Russian official said his country was worried about the violation of basic laws, interference in internal affairs by other countries and apparent support for coup d'etat.