The United States believes that Russian President Vladimir Putin's threatened retaliation against Ukraine over its drone attack last weekend has not happened yet in earnest and is likely to be a significant,

Ukraine and Russia, earlier this month, agreed to exchange 1,000 prisoners of war and civilian detainees each in a rare moment of cooperation in more than three years of war.

Russia and Ukraine swapped hundreds more prisoners on Sunday, the third and last part of a major exchange that reflected a rare moment of cooperation in otherwise failed efforts to reach a