By Phil Stewart
HALIFAX, Nova Scotia (Reuters) - U.S. Defense Secretary Chuck Hagel announced on Friday the Pentagon's first Arctic strategy to guide changes in military planning as rapidly thawing ice reshapes global commerce and energy exploration, possibly raising tensions along the way.
Ice on the Arctic Ocean shrank last year to its lowest levels since satellite observations began in the 1970s, and many experts expect it will vanish in summers by mid-century due to climate change.
As the sea ice thaws, ships are increasingly using a shortcut between the Atlantic and the Pacific, and competition is intensifying for Arctic oil and gas, estimated at around 15 percent and 30 percent respectively of undiscovered reserves.
Hagel, addressing a security forum in Canada, said the military would "evolve" its infrastructure and capabilities and would keep defending U.S. sovereignty in and around Alaska while working to help ensure freedom of the seas.
Part of strategy would also include bolstering U.S. military ties with fellow Arctic nations, including Russia.
Russian President Vladimir Putin has described the Arctic as crucial to Russia's economic future and security, and has redeployed forces to the region.
"Throughout human history, mankind has raced to discover the next frontier. And time after time, discovery was swiftly followed by conflict," Hagel said.
"We cannot erase this history. But we can assure that history does not repeat itself in the Arctic."
In September, Putin announced Russia was reopening a Soviet-era military base in the Arctic, part of a drive to make the northern coast a global shipping route and secure the region's vast energy resources.
Meanwhile, the U.S. military has an extensive presence in Alaska, with around 27,000 U.S. forces there. Hagel noted that the U.S. military had ski-equipped C-130s and nuclear submarines with decades of operations in polar regions.
Beyond potential tensions over energy, Hagel noted that increased tourism and commercial activity on Arctic sea routes would increase the risk of accidents.
"Migrating fish stocks will draw fishermen to new areas, challenging existing management plans," Hagel said.
Hagel said the U.S. military would adapt infrastructure and capabilities "at a pace consistent with changing conditions." He did not offer specific details or promise specific resources, and the speech came as the Pentagon reels from funding shortfalls.
One U.S. official, briefing reporters on condition of anonymity, played down any current tensions with Russia over the Arctic. The official noted that the U.S. Coast Guard had experienced "quite positive" interaction with its Russian counterparts over the years.
Another U.S. official said the strategy assessed a relatively low military threat in the Arctic, "and we don't see that changing in the near term."
Hagel stressed the opportunity for strengthening ties in the region.
"By taking advantage of multilateral training opportunities with partners in the region, we will enhance our cold-weather operational experience, and strengthen our military-to-military ties with other Arctic nations," he said.
"This includes Russia."
(Reporting by Phil Stewart; Editing by Vicki Allen)