(CNN) A massive US-led military exercise involving 18,000 soldiers from 19 nations, primarily NATO members, kicked off Sunday along the alliance's eastern border.

Saber Strike 18 will take place until June 15 in Poland, Latvia, Lithuania and Estonia.

The multinational exercise, which is being held for the eighth time, "is the platform to validate our collective capability to rapidly respond to and reinforce allies in a time of crisis," said US Army Europe. It is "a clear demonstration of the commitment and solidarity of the alliance."

The exercise will be conducted amid heightened tensions with Moscow, which views any NATO military activities along its border negatively, maintaining that it increases "mutual distrust."

Poland recently revealed it is considering a proposal for a permanent deployment of US troops to the country -- a move Russia denounced as "gradual expansion of NATO" towards its borders.

Read More