Dockworkers on Canada’s west coast are on strike again after a contract reached last week was rejected by the union.

The International Longshore & Warehouse Union caucus has voted down the terms recommended by a federal mediator, the union representing 7,000 workers said in a release Tuesday. Workers were set to return to the picket line at 4:30 p.m. Vancouver time.

The union’s decision means the resumption of a labor dispute that had paralyzed trade out of west coast ports including Vancouver, Canada’s busiest. Canadian Manufacturers & Exporters, a trade group, had estimated the strike caused daily trade disruptions amounting to C$500 million ($380 million).

An tentative four-year agreement was reached on July 13 between the union and the BC Maritime Employers Association with the support of the federal government. But it was subject to ratification by both sides.

Job security was a key issue. “The ILWU Canada Longshore caucus does not believe the recommendations had the ability to protect our jobs now or into the future,” the group said.

Alberta Premier Danielle Smith called on the federal government to draft legislation to force the workers back. Prime Minister Justin Trudeau’s government has been reluctant to do that, given that it has an alliance in parliament with a union-friendly opposition party.

“Albertans and Canadians cannot afford to have hundred of millions of dollars daily in products delayed at these ports,” Smith said on Twitter. “And the longer this strike continues, the more Canada’s credibility as a reliable trading partner is damaged.”

“In rejecting this tentative agreement, ILWU leadership is choosing to further harm Canada’s economy, international reputation and most importantly, to Canadians, their livelihoods and all those that rely on a stable supply chain,” the maritime employers’ group said in a release.

(Updates with Alberta premier’s comments)