By Lee Carter
BBC News, Toronto
All large ships entering the Northwest Passage and other Arctic waterways must register with the Canadian Coast Guard first, Canada's PM says.
Prime Minister Stephen Harper made the announcement during a three-day visit to the Arctic to bolster Canadian sovereignty claims.
Canada's claim over the area, which has rich reserves of oil and gas, is disputed by many countries.
The US in particular insists the passage is an international waterway.
'Authority and protection'
Mr Harper is brandishing his credentials as a leader willing to protect Canada's claims of sovereignty just days before he is widely expected to call a general election.
With a chilly wind blowing from the Beaufort Sea and a Coast Guard icebreaker behind him, Mr Harper emphasised the importance of defending his country's interests in the Arctic.
"Sovereignty as you know is not an abstract notion. It conveys a source of authority and protection," he said.
Mr Harper said such protection would now require all large ships entering Canadian arctic waters to register with the country's Coast Guard.
"These measures will send a clear message to the world," he said.
"Canada takes responsibility for environmental protection and enforcement in our Arctic waters."
Melting ice offers the possibility that the Northwest Passage may at last become navigable, linking the Atlantic and Pacific oceans.
That prospect, along with the Arctic's many hidden resources, has led to a number of regional countries - such as Russia, the US, Denmark, Iceland and Norway - scrambling to stake their claims.