The company behind the planned Keystone XL oil pipeline said it had to re-apply for a construction permit in South Dakota because of approval delays.

Pipeline company TransCanada submitted its application to the U.S. federal government to build Keystone XL across the Canadian border into the United States more than six years ago. It said Monday it had to reapply for a construction permit in South Dakota because the initial permit has now expired.

State law requires TransCanada certify its application with the South Dakota Public Utilities Commission if construction hasn't started within four years of the certification.

"Keystone XL was great news for South Dakotans four years ago," the company said. "It is even better news today."

South Dakota Gov. Dennis Daugaard has expressed support for a project that's become a scapegoat for environmental groups worried about the fallout from the embrace of the heavier type of Canadian crude oil designated for Keystone XL.

A spill of Canadian crude oil in Michigan in 2010 was among the costliest incidents of its kind in North American history.

TransCanada said its potential Keystone XL customers are still behind the project "and thousands of American men and women and their families are waiting for the work to begin."