Winnipeg Transit unveiled its first zero emission bus on Wednesday. 

But while the city expects to receive dozens more zero-emission buses over the next few years, supply chain issues, budget pressures and looming tariff threats have thrown the city's plans to phase out its diesel fleet into doubt.

Erin Cooke, manager of Transit's transition to zero-emission bus program, says the city will test two types of buses — hydrogen fuel cell and battery electric — in 40-foot and 60-foot sizes. 

The fuel c…