CALGARY -- Canada has mounted its biggest campaign yet to sell the United States on the energy security benefits of the oil sands as Washington debates new environmental policy, the country's energy minister said on Friday.

Canadian Natural Resources Minister Lisa Raitt said she and her staff are lobbying interests in the United States at all levels, trying to send the message that the huge heavy-oil resource in Alberta is being developed responsibly and that U.S. input on environmental fixes is welcome.

The push comes as environmental groups have intensified their own campaigns warning of the impact of oil sands development on climate, water, land and local communities on both sides of the border.