NATO’s Saber Strike 18 exercises involving some 18,000 troops from 19 nations have kicked off in Poland and the Baltic states, as the Western alliance looks to boost readiness on its eastern flank.

The June 3-15 maneuvers come as Poland has indicated it is considering a proposal to host a permanent contingent of U.S. troops in the way that Germany and Italy have done since World War II.

The United States leads a multinational NATO battle group in Poland, while allies Germany, Britain, and Canada command three others in the Baltic states of Estonia, Latvia, and Lithuania, where the Saber Strike maneuvers will be held.

“The long-standing U.S. Army Europe-led cooperative training exercise is designed to enhance readiness and interoperability among allies and regional partners,” the U.S. Army said.

It added that the U.S.-led annual maneuvers will “demonstrate the alliance’s determination and ability to act as one in response to any aggression.”

The United States and NATO have bolstered their presence in Poland and elsewhere on the alliance’s eastern flank since Russia's 2014 annexation of Crimea from Ukraine and its support for separatists in eastern Ukraine.

An “information document” by the Polish Defense Ministry seen by news agencies suggests that Warsaw could spend $1.5 billion to $2 billion to help cover the cost of permanently basing a U.S. tank unit in Poland.

Russia immediately attacked the proposal, saying such a deployment "in no way creates security and stability on the continent."

NATO has deployed some 6,000 troops in the region, and the U.S. Army has established a new European headquarters in Poland to command the forces.

With reporting by AFP and The Stars & Stripes