Canada hedges on 2010 start for emissions rules

* Says Canada has to harmonize with U.S. rules

* Cites U.S. proposal looking at 2012 or later

* Environmental group opposes delay

By Allan Dowd

VANCOUVER, British Columbia, May 28 (Reuters) - Canada's rules for cutting greenhouse gas emissions may not come into effect by 2010 as had been planned, Environment Minister Jim Prentice said on Thursday.

The rules may be ready by next year but the implementation timing will depend on discussions with other countries -- including the United States, Canada's largest trading partner-- for economic competitiveness reasons, Prentice said.

Prentice, speaking to reporters from London, cited a major climate change proposal now before Congress in Washington that sees regulations for different sectors of the U.S. economy beginning to take effect between 2012 and 2016.

"We will need to ensure that the application dates for Canadian climate change policies are harmonized with the Untied States or at least that we give close consideration to how and when individual sectors of the American economy will be regulated," Prentice said.

The Conservative government has pledged to cut Canada's carbon emissions 20 percent from 2006 levels by 2020. In a shift in position last year it also said it would work to develop a North American-wide cap and trade system to limit emissions of greenhouse gasses, blamed for climate change.