(CNN) President Donald Trump again threatened to tear up the North American Free Trade Agreement if Canada doesn't concede to new terms.

In a Saturday morning tweet, Trump said there is "no political necessity to keep Canada in the new NAFTA deal," referring to the tentative bilateral agreement the United States reached with Mexico earlier this week.

"If we don't make a fair deal for the U.S. after decades of abuse,Canada will be out," Trump said. He also urged Congress not to "interfere" with negotiations "or I will simply terminate NAFTA entirely & we will be far better off."

The United States and Mexico announced a preliminary bilateral trade deal on Monday after resolving an issue over auto manufacturing. Canadian officials rejoined the talks this week.

But the fate of NAFTA became uncertain Friday when the United States and Canada failed to come to an agreement on rewriting the three-nation trade pact before a US-imposed deadline that would have allowed them to sign a new deal before Mexico's president-elect, Andres Manuel Lopez Obrador, takes office on December 1.

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