The White House has called a Russian convoy's move into Ukraine a "flagrant violation" of the country's sovereignty and urged Russia to remove it or face more economic sanctions.
White House deputy national security Ben Rhodes told reporters that sending the convoy into Ukraine adds to the escalation of the conflict "in a dangerous way."
The United States plans to discuss the situation with the UN Security Council later today, he added.
More top news
A man who helped officers apprehend a suspected drug dealer by sticking out his foot and tripping him has been hailed a "legend" by police.
Sarah Bartlett was surprised when she received an anonymous card containing £100 as a reward for doing an "amazing job" as a mum
A cat who prowls a station on the hunt for mice has been promoted to become the official pest control manager.