Secretary of State John Kerry stated this during a phone conversation with his Russian counterpart Sergei Lavrov.
"Kerry urged Lavrov to stop the flow of heavy weapons and rocket and artillery fire from Russia into Ukraine, and to begin to contribute to deescalating the conflict," a State Department official said.
"He (Kerry) did not accept Foreign Minister Lavrov's denial that heavy weapons from Russia were contributing to the conflict," said the State Department official, who spoke on condition of anonymity.
"The Secretary underlined our support for a mutual cease fire verified by the OSCE (Organization for Security and Co-operation in Europe) and reaffirmed our strong support for the international investigation to show the facts of MH17," the official said.
Kerry also provided an update on his meetings in the Middle East and Paris this past week and the ongoing efforts to achieve a ceasefire, the official added.
Meanwhile, US intelligence agencies provided images as evidence that Russian forces have fired across the border at Ukrainian military forces, and that Russia-backed separatists have used heavy artillery, provided by Russia, in attacks on Ukrainian forces from inside Ukraine.
One of the images shows ground scarring at a multiple rocket launch site on the Russian side of the border oriented in the direction of Ukrainian military units within Ukraine.
The wide area of impacts near the Ukrainian military units indicates fire from multiple rocket launchers and can also be seen.
Another image shows self-propelled artillery only found in Russian military units, on the Russian side of the border, oriented in the direction of a Ukrainian military unit within Ukraine.
The pattern of crater impacts near the Ukrainian military unit indicates strikes from artillery fired from self-propelled or towed artillery and vice multiple rocket launchers.
The third image shows ground scarring at two multiple rocket launch sites oriented in the direction of Ukrainian military units.
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