Washington, July 12 -- Canada will face a 35% tariff on exports to the United States starting August 1, President Donald Trump said Thursday in a letter to Prime Minister Mark Carney. It was the latest of more than 20 such letters issued by Trump since Monday, as he continues to pursue his trade war threats against dozens of economies. Canada and the US have been locked in trade negotiations in hopes of reaching a deal by July 21, but the latest threat appeared to have shifted that deadline. Both Canada and Mexico are trying to find ways to satisfy Trump so that the free trade deal uniting the three countries -- known as the USMCA -- can be put back on track. "Throughout the current trade negotiations with the United States, the Canadian government has steadfastly defended our workers and businesses. We will continue to do so as we work towards the revised deadline of August 1," Carney posted on social media platform X Thursday night. The United States-Mexico-Canada Agreement replaced the previous NAFTA accord in July 2020, after Trump successfully pushed for a renegotiation during his first term in office. It was due to be reviewed by July next year, but Trump has thrown the process into disarray by launching his trade wars after he took office in January....