Biden mum on Keystone

Vice President Biden has conveyed his opinion on the Keystone XL oil pipeline to President Obama but doesn't want to "step on the president's lines" by stating it publicly, he told a woman who asked him about the controversial construction project Wednesday in Iowa.

“I am vice-president,” Biden said, emphasizing the "vice," according to The Guardian. “So what I’ve learned to do, is not step on the president’s lines. I do have an opinion. I’ve made it clear to the president what my opinion is. But I am vice-president.”

It's not the first time the vice president has raised eyebrows while discussing the project on a rope line. During a trip to South Carolina last year, an environmental activist said Biden told her he supported rejecting the pipeline but was "in the minority," according to an email obtained by BuzzFeed.

The vice president's office did not confirm the exchange at the time, and told The Washington Post that Biden was awaiting the State Department's review of the project.

Asked about the project in a 2012 interview with KWQC-TV, Biden said the State Department was reviewing the project "to make sure it can be environmentally sound."

“It’s going to go through the process and it will be made on an environmentally sound basis,” he said.

Environmental groups have rallied against the pipeline, arguing a spill could have a disastrous environmental impact and that its construction would encourage tar sands extraction. But advocates of the project say the pipeline is more eco-friendly than shipping oil by rail, and construction would create jobs.

The White House has said it will not weigh in on the project until the conclusion of that review. In April, the State Department announced it was delaying that decision until after the midterm elections because of an ongoing court battle in Nebraska.