Mexico and Canada are putting aside their differences and forming a more united front as they try to head off US President Donald Trump’s threat to impose steep tariffs on them as soon as next week. Since winning the election in November Trump has repeatedly threatened his country’s two largest trading partners with tariffs of 25 per cent on all exports to the US in retaliation for what he says are rising levels of illegal immigration and the trafficking of the opioid fentanyl into the country.

Every day a flurry of parts and products are shuttled between Texas and Mexico, part of a cross-border supply chain to make everything from cars and heavy duty machinery to flat screen televisions. The future of that partnership,