A key American hurdle that experts feared could frustrate Ottawa's $4.5-billion offer to purchase the Kinder Morgan Trans Mountain oil pipeline has been surpassed.  

A U.S. national security review by the Committee on Foreign Investments in the United States, or CFIUS, has given the green light for Canada to buy the pipeline from Kinder Morgan. 

The review of the pipeline, set to be expanded to triple the flow of bitumen between Edmonton and Burnaby, was necessary because a section of the existing pipeline system, called the Puget Sound pipeline, also pumps oil from Abbottsford, B.C. to Washington state refineries.

Some, such as Green Party leader Elizabeth May, believed President Trump might use the security review as an excuse to expand a Canada-U.S. trade war to Canadian energy exports. But Kinder Morgan Canada confirmed late Friday that the U.S. review was passed, along with a recent ruling by the National Energy Board that the expansion project can begin construction on most sections between Alberta and B.C.

"We have received the required regulatory approvals necessary to close the sale of the Trans Mountain Pipeline system and the Trans Mountain Expansion Project (TMEP) to the Government of Canada," wrote Kinder Morgan spokesperson Ali Hounsell.

The pipeline expansion now faces two further hurdles.  First, KML shareholders will meet on August 30 to vote on Canada's offer to buy the existing Trans Mountain pipeline. Secondly, the expansion project faces a number of lawsuits from opponents, including First Nations, the City of Burnaby and the province of British Columbia.

The U.S. approval comes just a day after the RCMP enforced a court order on Thursday to remove the shelters from the "Camp Cloud" protest camp just outside the Kinder Morgan oil tank farm in Burnaby.  Eleven people were also removed from the camp during the arrests.