The new US special representative for Ukraine says Washington is actively reviewing whether to send weapons to help those fighting against Russian-backed rebels.
According to the representative, arming Ukrainian government forces could change Moscow's approach.
Last week, the US State Department urged both sides to observe the fragile ceasefire in eastern Ukraine.
The UN says more than 10,000 people have died since the eastern Ukraine conflict erupted in April 2014, soon after Russia annexed Ukraine's Crimea peninsula. The fighting has displaced more than 1.6 million people.
A ceasefire was agreed in Minsk in February 2015, but its terms are far from being fulfilled.
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