6 thousand Ukrainian and foreign military personnel will take part in the Rapid Trident exercise
Ukraine has begun joint military exercises with the United States and other NATO countries.
The country, which has been at war with Russian-backed separatists since 2014, has long sought closer integration with Western military forces in hopes of joining NATO one day.
A representative of the Ministry of Defense of Ukraine said that 4,000 Ukrainian and 2,000 foreign troops will take part in the Rapid Trident-2021 exercise, which will last until October 1.
"I believe that each of you will concentrate all your knowledge, will concentrate all your forces to show the aggressor that they have no chance," said the commander of the training of the Ukrainian forces Igor Palagniuk at the opening ceremony at the International Center for Peacekeeping and Security near Yarov in the west of the country.
The US military said in a statement that a brigade combat group of the Washington National Guard, deployed in Ukraine since April as part of a multinational training force, is participating in the exercise.
Military personnel from 12 countries are taking part in the exercises aimed at "increasing the level of functional interaction between allied and partner countries, as well as demonstrating combat readiness."
Meanwhile, on Monday, about 20 Russian warships began large-scale live-fire exercises in the Black Sea.