There's nothing in the narrative on the Keystone XL pipeline offered by Hillary Clinton the White House sees as necessarily disagreeable, a spokesman said.

Democratic presidential candidate and former Secretary of State Clinton explained her stance on the proposed oil pipeline from Canada in an opinion piece in online news forum Medium.

"We shouldn't be building a pipeline dedicated to moving North America's dirtiest fuel through our communities," she wrote. "We should be focused on what it will take to make America the clean energy superpower of the 21st century."

Clinton on the campaign trail in Iowa said the proposed pipeline was a distraction from addressing the challenges presented by climate change.

White House spokesman Josh Earnest on Wednesday said President Barack Obama is on the record as expressing skepticism about statements in support of the pipeline.

"I don't know that I can say that we agreed necessarily with everything that she included in her statement," he said on Clinton's position. "But there's nothing that has been widely reported that I would strenuously disagree with."

An executive order gives the U.S. State Department vetting power over the pipeline. Obama earlier this year vetoed legislation the White House said circumvents the normal vetting procedures for the pipeline.

Davis Sheremata, a spokesman for pipeline planner TransCanada, said statements describing Canadian oil sands, the type of oil designated for Keystone XL, as the dirtiest form of oil in North America are incorrect.

"The California Environmental Protection Agency Air Resources Board states there are 13 oil fields in California that generate more greenhouse gas emissions than Canadian diluted bitumen blends," he said in an emailed statement. "I would add that according to Environment Canada, the oil sands produce less than one fifth of one per cent of global greenhouse gas emissions -- an extremely small number."

Keystone supporters say it would lead to substantial North American economic stimulus, create more jobs and support energy security at a time when more Iranian crude oil is expected on the international market.

In June, Cynthia Quaterman, the former administrator for the federal Pipeline and Hazardous Materials Safety Administration, told delegates at a Houston summit sponsored by energy reporting agency Argus the Keystone XL pipeline might not fit in the U.S. oil landscape because of increased domestic production.