EDMONTON — Federal NDP leader Avi Lewis says Ottawa must place an export tax on Canadian energy to help negotiate a trade agreement with the U.S. amid an ongoing trade war. "We have things that the United States needs," said Lewis in an interview with CBC. "Sixty percent of the United States oil imports come from Canada. Critical minerals, potash. There are resources that the United States desperately needs." .Lewis, a vocal critic of Alberta's oil industry, said he has spoken with Prime Minister Mark Carney and "forcefully" made the case for his government to use Canada's leverage. "Six months ago, I think I was the only politician in Canada calling for export taxes on oil and gas," Lewis said. "We have now heard that call from former Prime Minister Jean-Créchin. We've heard it from former Alberta Premier Alison Redford. ""We heard it from a Toronto Star columnist recently, and so there is growing sense and growing pressure across the political spectrum that we need to use the leverage we have." .While many leaders have advocated for Ottawa to use Alberta's oil as leverage, the two most important voices on the matter, Carney and Alberta Premier Danielle Smith, have said they are not looking to do so. "Although I understand the need to respond strongly to these tariffs, I cannot think of a more disastrous policy decision than cutting off or taxing Alberta's oil to the United States," said Smith during an address directed to Canadians on Wednesday. "Doing so would absolutely devastate the Canadian economy." Smith wants Canadian and U.S. officials to return to the negotiating table quickly to avoid further escalation beyond the already announced mutual 50% tariffs. The federal government announced their retaliatory tariffs on Tuesday, and the plan did not include any actions involving Alberta oil or other Canadian energy resources. Carney has previously said he is not looking to use energy resources as a negotiating tool, claiming that Canada must maintain its global reputation as a reliable supplier and trading partner. However, on Saturday he teased the power that such an action could have. "I don't think they want us to stop sending any of that energy," Carney said.