MONTREAL -- Former Mexican president Vicente Fox says Donald Trump is blackmailing Canada and Mexico in order to exert maximum pressure to reach a new NAFTA deal.

The outspoken ex-politician says Canada and Mexico have to remain firmly united rather than give in to the U.S. president's demands for bilateral agreements with its two North American neighbours.

He says countries like Canada need to stand up against Trump's bullying behaviour and criticizes the "crazy horse" president for verbally attacking Prime Minister Justin Trudeau after the G7 meeting for stating Canada won't be pushed around.

Canada and Mexico have both announced retaliatory tariffs after the United States imposed tariffs on steel and aluminum on them and a host of other countries.

Fox says Mexico can also buy soybeans, yellow corn and dairy products from Brazil, Argentina and other countries to exert pressure on U.S. farmers.

He adds that imposed U.S. tariffs will raise prices for American consumers but won't destroy Mexico because the country has developed a solid consumer market and can shift exports to South America.

Fox says American trade actions will only further drive countries into the trading orbit of China, which is increasing its business relationships in Latin America.