Russia has insisted that Kiev pull back its troops from eastern Ukraine as it accused Washington of distorting an agreement to ease the most serious confrontation between Moscow and the West since the end of the Cold War.
"The Russian side once again insists on the immediate de-escalation of the situation in Ukraine's southeast, the pullback of units of the Ukrainian army and the start of a genuine internal Ukrainian dialogue involving all of the country's regions and political formations," the Foreign Ministry said on Wednesday.
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"Moscow is extremely surprised by the distorted interpretations by Kiev authorities as well as by our US partners of the contents of a declaration adopted in Geneva on April 17 as a result of a four-way meeting between representatives of Russia, the United States, the European Union and Ukraine."
The Russian Foreign Ministry said while the Geneva accord called on all "illegal armed units" to lay down arms, Kiev and Washington were turning a blind eye to what Moscow called continuing provocations by ultra-right militants in Ukraine.
"The Russian side continues to believe that our Western partners are serious when they declare their intention to facilitate a peaceful settlement of the political crisis in Ukraine," the foreign ministry said.
"Alas, the facts suggest the opposite however. We are still waiting for Kiev, which is responsible for establishing dialogue with Ukraine's regions, including in the southeast, to fulfil its promises."
Moscow said it had expected Joe Biden, the US vice president who visited Ukraine this week, to influence the Ukrainian authorities with an eye to ease the crisis.
"However, immediately after his departure from the Ukrainian capital it was announced there that an 'anti-terrorist operation' in Ukraine's eastern regions would resume," the foreign ministry said.
Earlier, Russia's top diplomat Sergey Lavrov issued a blunt warning it would respond if its interests were attacked in Ukraine, in a sign Moscow was upping the ante in the crisis.
In an interview with Russia Today, the Russian foreign minister said that "Russian citizens being attacked is an attack against the Russian Federation".
The comments were released after the Vitaly Yarema, Ukraine's acting first deputy prime minister, said "appropriate measures" were being taken against pro-Russian separatists in the country's east.
"We have obtained the support of the United States, that they will not leave us alone with an aggressor. We hope that in the event of Russian aggression, this help will be more substantive."
Lavrov said that it was no coincidence that the resumption of operations came after Biden's visit, and charged that the US was "running the show".
The US also announced on Tuesday that it was sending 600 troops to Poland to begin a series of military exercises in four countries across eastern Europe.
The exercises are part of an effort announced last week aimed at reassuring NATO allies of the US's commitment to the region's defence.