If the Obama administration rejects the Keystone XL pipeline, it would be a significant thorn in Canadian-U.S. relations, Alberta's premier said Wednesday.

Premier Alison Redford was in Washington for her fourth trip to lobby on behalf of a pipeline that Canada sees as critical to its economic well-being. The Obama administration is considering whether to approve the pipeline, which would carry 800,000 barrels of oil a day from Alberta across six U.S. states to the Texas Gulf Coast, which has numerous refineries. A decision is expected later this summer.

"It would become something that we would continue to talk about," Redford said of a possible rejection during a telephone interview with The Associated Press. "It would be a continuing issue."

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