TransCanada Corp. lost an appeal Friday to suspend a U.S. trial court injunction that halted continued construction of its proposed Keystone XL oil export pipeline last November.

A panel of the Ninth U.S. Circuit Court of Appeals upheld the injunction. The decision, a ruling on a motion that TransCanada presented as urgent, said the stop-work order will stand until the appeal court decides on the merits of the case.

After the setback, TransCanada only said in a brief statement, "We are currently assessing the decision and considering our options moving forward."

The injunction, handed down by U.S. District Judge Brian Morris in Montana, bans physical construction work but allows planning and preparation work to continue while the U.S. State Department updates environmental aspects of its Keystone approval.

According to TransCanada's unsuccessful motion, leaving the injunction in place could delay construction by a year, cause $949 million in financial losses and postpone 6,600 jobs in the United States.

Keystone's environmental and native opponents predicted Friday's legal setback would turn out to be the death knell for the $8 billion delivery plan for 830,000 b/d of exports from Canada's top natural gas user, Alberta thermal oilsands production.