Russia has vowed to retaliate against a plan by Norway to more than double the number of U.S. Marines stationed in the country.
The Russian Embassy in Oslo issued the warning on June 14, two days after Norway announced it will ask the United States, its NATO ally, to send 700 Marines starting next year.
The move came amid increasing wariness among nations bordering Russia following Moscow's annexation of Ukraine's Crimea Peninsula in 2014.
The Russian Embassy said that Norway’s plan, if realized, would make Norway “less predictable and could cause growing tensions, triggering an arms race, and destabilizing the situation in northern Europe."
"We see it as clearly unfriendly, and it will not remain free of consequence," it said in a statement.
Some 330 U.S. Marines currently are scheduled to leave Norway at the end of this year after an initial contingent arrived in January 2017 to train for fighting in winter conditions. They were the first foreign troops to be stationed in Norway, a member of NATO, since World War II.
Norwegian Foreign Minister Ine Eriksen Soereide told reporters on June 12 that the additional U.S. troops would be based closer to the border with Russia in the Inner Troms region in the Norwegian Arctic, about 420 kilometers from Russia, rather than in central Norway.
Soereide also said that the decision to increase the U.S. presence has broad support in parliament and does not constitute the establishment of a permanent U.S. base in Norway.
The initial decision to welcome the Marines irked Russia, with Moscow warning that it would worsen bilateral relations with Oslo.
NATO's massive exercise Trident Juncture 18 is due to take place in and around Norway in October-November.
All 29 NATO allies, as well as Finland and Sweden, will participate in the drills, which will involve some 40,000 troops, 70 ships, and 130 aircraft.