KYIV, July 5 - Ukraine, the United States, Poland and Lithuania will hold a large military exercise in the western part of Ukraine later in July, the Ukrainian military said on Monday, the second round of war games involving Kyiv and foreign partners in a month, Reuters reported.

The drill, Three Swords-2021, will involve more 1,200 servicemen and more than 200 combat vehicles and will last from 17 to 30 July at Yavoriv training ground in Lviv region.

"Three Swords-2021 create favorable conditions for the development and effective coordination of units of partner states, in order to improve the quality and increase the level of combat capabilities," the military said in a statement.

Last week, Ukraine and the United States started a military exercise, Sea Breeze, involving more than 30 countries in the Black Sea and southern Ukraine, despite Russian calls to cancel the drills.

Sea Breeze 2021 follows a rise in tensions between NATO and Moscow, which said last month it had fired warning shots and dropped bombs in the path of a British warship to chase it out of Black Sea waters off the coast of Crimea.

President Volodymyr Zelenskiy said on Thursday that accession to NATO is a matter of security for Ukraine, but admitted the country has been lagging in some reform effort to do so.

"NATO is about security, after all. We've been treating it as a political issue for many years, for 13 years now, which includes constitutional amendments and [assumptions on] when we might see ourselves in NATO," Zelensky said in an interview with the 1+1 television channel on Thursday.

"Just support for Ukraine's territorial integrity isn't enough on the part of its Western partners," Zelensky said.

"What matters isn't so much joining NATO and receiving a NATO Membership Action Plan as whether Ukraine will be able to oppose any escalation on the part of the Russian Federation," he said.

Relations between Kyiv and Moscow plummeted after Russia seized Crimea and over Russia's support for a separatist rebellion in eastern Ukraine. (rt/ez)