CALGARY - A union representing pipefitters and plumbers has written to U.S. President Barack Obama urging him to approve the Keystone XL pipeline.

The United Association represents 52,000 workers in Canada, some of whom will be responsible for building the pipeline and maintaining it once it's complete.

John Telford, director of Canadian affairs at the union, says approval of the $5.3-billion project will be a catalyst for many economic benefits in both the United States and Canada.

Other Canadian labour groups, such as the Alberta Federation of Labour, have been concerned Keystone XL will mean fewer high-paying jobs in Canada.

They would prefer oilsands bitumen be processed into a more valuable product in Canada than shipped south of the border to be upgraded.

Last week the U.S. State Department issued a draft environmental report that did not flag any major concerns about the pipeline being built.