Democratic US presidential candidate Hillary Clinton said on 22 September that she opposes the Keystone XL oil pipeline, TransCanada Corp's proposed pipeline from Canada's oil sands to Gulf Coast refineries.

Clinton, the former US secretary of state, had not until now stated whether she favours approval of the pipeline, telling an audience at a campaign stop in Des Moines, Iowa that she had not wanted to "interfere" with the Obama administration's ongoing decision over the pipeline.

"I thought this would be decided by now and therefore I could tell you whether I agreed or I disagreed. But it hasn't been decided and I feel now I've got a responsibility to you and other voters who ask me about this," Clinton said after a member of the audience asked her about her stand on the issue.

"I think it is imperative that we look at the Keystone pipeline as what I believe it is. A distraction from the important work we have to do to combat climate change and unfortunately from my perspective one that interferes with our ability to move forward to deal with other issues. Therefore, I oppose it," Clinton said.

Clinton had said on 17 September that the Obama administration's decision on whether to approve the Keystone XL pipeline oil pipeline was overdue and she "can't wait too much longer" to say where she stands on the issue.

The White House said in August the US State Department continued to review TransCanada Corp's proposed Keystone XL pipeline.