Brussels, October 3 (RHC)-- NATO is planning to conduct its biggest military exercise since the Cold War, drawing as much as 45,000 troops in Norway, Secretary General Jens Stoltenberg says.

Speaking at the NATO headquarters in Brussels on Tuesday, the secretary general said in a statement that the maneuver seeks to practice defense operations against a "fictional" enemy, adding that "all members of the Organization for Security and Cooperation in Europe, including Russia, have been invited to send observers."

The war games, named Trident Juncture 18, will assemble troops from 31 NATO allies and partners along with 50 aircraft, 70 vessels and around 10,000 land vehicles in a two-month-long exercise focused primarily in central and eastern Norway, aiming to train "troops of the NATO Response Force " and improve joint-force cooperation, according to a Norwegian Armed Forces statement.

Shortly before Stoltenberg's remarks, United States Defense Secretary Jim Mattis vowed "iron-clad" commitment to the transatlantic alliance, adding that "every NATO ally is awake today to the reality of Russia's malicious behavior. Every ally has now increased defense spending."

The massive military maneuvers come amid rising tensions between the West and Russia over Moscow's alleged interference in Ukraine and a military build-up in the Arctic.  Russia denies the allegation.

NATO has subsequently increased activity around Russia in the past four years, deploying troops in Eastern Europe and in the Baltic states.

Contrarily, Moscow has expressed its own concerns over an ever-growing military build-up on NATO's northern flank, reacting angrily to Oslo's call for Washington to double the number of U.S. Marines in the country.