That letter started a 90-day required notice period for Congress before the president can legally sign a new deal.
Trumka also said that the reimagined North American Free Trade Agreement Trump has been touting would have to include Canada in order to earn his organization's endorsement. "Congress should not interfere with these negotiations or I will simply terminate NAFTA and we will be better off", he threatened, according to The Wall Street Journal on 1 September. US and Canadian negotiators worked throughout the week on adding Canada to Friday's notice, but the negotiations failed to produce an agreement ahead of Trump's own Friday deadline.
On a separate footing, the USA is now considering imposing new tariffs on $200 billion of imports from China on 7 September, following the conclusion of its public hearings with the American companies on China's theft of intellectual property and forced transfer of technology.
"The updated NAFTA agreement, especially the US-Mexican deal will be supported by business for nearly the relief it gives because the uncertainty was killing investment plans", according to Simon Evenett from St Gallen University in Switzerland.
Continetti said the key to Trump's recent trade negotiations was concentrating on Mexico and leaving Canada to one side.
Any deal with Canada would be "totally on our terms", the Toronto Star quoted Trump as saying in an off-the-record aside during an interview with Bloomberg News. But the limits of Trump's leverage were also becoming clear with the president still needing to get any agreement through a Congress that has concerns about any pact that does not include Canada.
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"Anything other than a trilateral agreement won't win congressional approval and would lose business support", President and CEO of the U.S. Chamber of Commerce, Thomas Donohue, said Friday in a statement.
Trump's attack came just two days ahead of another round of talks with Mexico and Canada on NAFTA, which Trump believes has cost American factory jobs. "If we do not make a fair deal for the USA after decades of abuse, Canada will be out", Trump tweeted.
U.S. -Canadian talks over the 25-year-old trade pact are set to resume on Wednesday.
The president said Saturday on Twitter that there was "no political necessity" to keep Canada in NAFTA.
Continetti pointed out that Trump's willingness to brandish America's economic power is working elsewhere. The White House set a deadline for Friday because it wanted to notify Congress in time for Mexican President Enrique Pena Nieto to sign the accord before his successor, Andres Manuel Lopez Obrador, takes office on December 1.
The union president also said the current NAFTA deal has had a "devastating effect" on American workers since its inception in 1994. The Canadian government found it hard to agree to the US' demands once they were reported in domestic media. Ottawa does have other complaints. And Congress, which has to approve any NAFTA rewrite, might refuse to endorse a deal that excludes Canada.