Norway has announced it is to allow more than 300 US troops to be stationed on its soil for a trial period in 2017.
It represents a shift from the peacetime policy of the Nato member, which shares a border with Russia, of prohibiting the posting of foreign troops in Norway.
Norway's defence minister emphasised its close ties with the US.
Tensions have been increasing. Last week a flotilla of Russian warships sailed past Norway en route to Syria.
Meanwhile, Finland has strengthened its military ties with the US and Moscow has warned of "consequences" if Sweden decides to join Nato.
The 330 US marines will be stationed for a trial period from January at the Vaernes military base just east of Trondheim, Defence Minister Ine Eriksen Soereide announced on Monday.
"This US-initiative is welcome and also fits well within ongoing processes in Nato to increase exercises, training and interoperability within the Alliance," she said.
"The defence of Norway is dependent on allied reinforcements, and it is crucial for Norwegian security that our allies come here to gain knowledge of how to operate in Norway and with Norwegian forces," she added.
The US already stores large amounts of military equipment in caves in Norway.
The Russian embassy in Norway reacted with surprise to the move when reports emerged on Friday.
"Taking into account multiple statements made by Norwegian officials about the absence of threat from Russia to Norway, we would like to understand why Norway is so much willing to increase its military potential, in particular through the stationing of American forces in Vaernes," spokesman Maxime Gourov said in an email sent to AFP news agency.
The small opposition Socialist Left party reportedly criticised the move, saying it would have been better for Norway to reinforce its own defences.
Conflicts in Ukraine and Syria have ratcheted up tensions between Russia and the West.