WASHINGTON—A U.S. lawmaker says he’s hearing that President Barack Obama is about to reject the Keystone XL pipeline, after years of delay and debate.

Sen. John Hoeven, a vocal supporter of the Canada-to-Texas project and a Republican critic of the president, seems an unlikely candidate to announce the long-awaited decision. But on Tuesday, the North Dakota lawmaker told the Senate that’s what he’s hearing from his sources.

Hoeven said he believes Obama, in the hope of stifling criticism, will make the announcement during the August congressional break.

The president has vetoed a Keystone XL bill in the past but has never definitively slammed the door shut on the project through the normal regulatory process.

Hoeven says rejection makes no sense on environmental grounds and would disadvantage the oil industry in Canada, a friendly U.S. neighbour, even as the recent international nuclear deal help build Iran’s energy industry.

Keystone XL would carry about one-quarter of the oil exported by Canada to the U.S. each day and would ease potential bottlenecks on rail lines. Its U.S. opponents, however, argue it would help develop one of the world’s dirtiest sources of oil.

The issue has become a fault line in the U.S. debate over climate change and energy politics. Republicans staunchly support the project, which has divided Democrats.

Asked about Hoeven’s remarks, the Canadian federal government issued a statement defending the project but said it would refrain from interfering in the American debate.

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