WASHINGTON — A group of 16 US state governors and the premiers of two Canadian provinces on Wednesday called on the leaders of both countries to end the cross-border vaccine requirement that sparked protests and briefly closed trade routes.

Protests in which demonstrators at one point blocked border crossings and truckers have clogged the streets of downtown Ottawa for nearly three weeks were sparked by rules mandating Covid vaccines to cross the US border.

In a letter released by the office of Montana Governor Greg Gianforte, a signatory, the state and provincial leaders said exemptions to the requirement should be reinstated for the sake of both countries’ economies.

“The timing of your decision to terminate the vaccine and quarantine exemptions could not have been worse, as North America already faces grave supply chain constraints,” the letter addressed to US President Joe Biden and Canadian Prime Minister Justin Trudeau said.

“These constraints, combined with increasing inflation, place significant burdens on the residents of Canada and the United States.”

All 16 US governors who signed are members of the opposition Republican party. They were joined by Alberta Premier Jason Kenney and Saskatchewan Premier Scott Moe, who has endorsed the truckers’ convoy.

The trucker movement at its peak included blockades of a half dozen border crossings — including a key trade route across the Ambassador Bridge between Windsor, Ontario and Detroit, which was reopened after police cleared demonstrators over the weekend.

The US economy has struggled with decades-high inflation and shortages of components and workers, including truck drivers, over the past year, harming Biden’s approval ratings. Canada saw its price increases hit a 30-year high last month.