US Secretary of State John Kerry has accused Russian leaders of lying to him about Moscow's involvement in the conflict in Ukraine.
"Russia has engaged in a rather remarkable period of the most overt and extensive propaganda exercise that I've seen since the very height of the Cold War," Kerry told a Senate committee in Washington on Tuesday.
"And they have been persisting in their misrepresentations, lies, whatever you want to call them, about their activities there to my face, to the face of others, on many different occasions."
Kerry has met multiple times in European cities with Russian Foreign Minister Sergey Lavrov since the Ukraine crisis erupted in early 2014.
Asked whether Moscow was lying when it denied that there were Russian troops or weapons in Ukraine, Kerry replied: "Yes."
The Obama administration is discussing whether to increase its support to Kiev to include lethal weapons to help the army battle pro-Russia rebels.
The Pentagon will deploy between five and 10 troops to western Ukraine to provide a second round of combat medical training to the Ukraine military there, a U.S. military official told Associated Press on Tuesday.
Meanwhile, Britain's Prime Minister David Cameron announced that his country would also send servicemen to train Ukrainian forces.
Up to 75 military personnel will be deployed as part of an operation lasting up to six months, the defence ministry confirmed separately. This will exclude the supply of lethal equipment.
A peace deal agreed to by Russia, Ukraine, France and Germany earlier this month has not settled the conflict over the territory's future. On Tuesday, the foreign ministers of the four nations met in Paris in a fresh push to salvage the plan.
Last week, Ukrainian President Petro Poroshenko called for U.N. peacekeepers to be deployed to monitor a cease-fire in war-weary east Ukraine, a proposal that pro-Russia rebels swiftly said would be in breach of a peace deal.