The United States will invest billions of dollars on ships that break up polar ice to challenge Russia’s dominance in the Arctic.

American navy commanders have repeatedly criticised the lack of any clear strategy from the Pentagon for the region, especially because ice-melting conditions are opening up opportunities for merchant shipping lanes. The coastguard has only two operational icebreakers, compared with 45 that Russia owns. China has one but has an ambitious building programme that has raised concerns in the US.

James Mattis, the US defence secretary, declared in a national defence strategy document in January that the Pentagon’s top priority was to prepare for a “great power competition” from Russia and China. However, officials warned that in the Arctic the military was lagging behind