An environmental impact study into the Keystone XL pipeline project is likely to be announced on Friday afternoon, a U.S. media report says.

CNN cites two senior administration officials and another unidentified source familiar with the timing.

Once the results are out, eight U.S. agencies will examine them, then send their observations to Secretary of State John Kerry. President Barack Obama would then decide whether or not to approve the pipeline.

A final decision may not come for several months, but this study is seen as a critical step in determining whether the project will go ahead.

If ultimately approved, the TransCanada Corp. pipeline would ship bitumen from Alberta's oilsands to refineries on the U.S. Gulf Coast.

Supporters say the pipeline would reduce imports from overseas and create jobs while opponents warn against potential environmental damage.

One diplomat in Washington told The Canadian Press this week that the results are "going to be positive for the project."

Earlier this month, Foreign Affairs Minister John Baird was in Washington pleading for a quick decision. He said enough time had been lost on the project and didn't want to see another construction season wasted.

Kerry responded that there would be no fast-tracking the process.