An environmental dispute between the U.S. and Canada is coming to a head, with a lumber trade agreement between the two countries set to expire at the end of the month. Enviros and many U.S. policymakers say the Canadian government unfairly subsidizes the logging of old-growth timber, undercutting the market for wood in the U.S., while the Canadian government and logging companies deny the charge. Canada has threatened to choke the supply of natural gas to Western states if the U.S. limits imports of Canadian softwood, which currently account for about one-third of the softwood lumber supply in the U.S.