Toronto ? Canada announced plans Monday to increase its Arctic military presence in an effort to assert sovereignty over the Northwest Passage – a potentially oil-rich region the United States claims is international territory.

Prime Minister Stephen Harper said six to eight patrol ships will guard what he says are Canadian waters. A deep water port also will be built in a region the U.S. Geological Survey estimates has as much as 25 percent of the world’s undiscovered oil and gas.

“Canada has a choice when it comes to defending our sovereignty over the Arctic. We either use it or lose it. And make no mistake, this government intends to use it,” Harper said.

As global warming melts the passage – which now is only navigable during a slim window in the summer – the waters are exposing unexplored resources such as oil, fishing stocks and minerals, and becoming an attractive shipping route.