Ukraine on Monday launched joint military exercises with the United States and a host of other NATO countries as its bitter rival Russia gears up for its own war games on the EU border.
The annual Rapid Trident military exercises, taking place in the western Ukrainian city of Yavoriv until September 23, involve an "unprecedented" number of 2,500 soldiers from 15 countries, the Ukrainian military said in a statement.
"Today, your support is very important for us. The experience of our colleagues is extremely valuable for the Ukrainian army," Colonel Sergei Litvinov, the exercises co-director on the Ukrainian side, said.
The Ukraine drills began days ahead of Moscow's massive military exercise "Zapad 2017" ("West") in neighbouring Russia and Belarus.
The event has caused alarm in the Baltic states and Poland and drawn criticism from the United States and NATO for a lack of transparency.
Russia has said the exercises will involve about 12,700 Russian and Belarusian troops and are "purely defensive" in nature, but critics say there could be as many as 100,000 soldiers taking part.
NATO has also deployed about 1,000 soldiers in each of the Baltic states and Poland in response to growing concern over Russian intentions after Moscow's 2014 annexation of Crimea from Ukraine.
The peninsula annexation was followed by Russian-backed insurgency in the Ukraine's war-torn east that has killed more than 10,000 people.
Kiev and the West have accused Russia of buttressing the rebels and sending in regular troops across the border, claims Moscow has repeatedly denied.
On Friday, Kiev reported the first combat death since the warring sides agreed to a new truce in August after a series of previous such deals failed to bring any tangible results.