The White House has rejected a proposal to extend a multi-billion dollar pipeline to bring Canadian oil to US refineries.<br /><br />Stephen Harper, Canada's prime minister, says he is profoundly disappointed by the decision.<br /><br />However, environmentalists had argued it will cause major problems for several states and labour unions say the project would create thousands of jobs.<br /><br />Al Jazeera's Rosiland Jordan reports from Washington.
