Investors are waking up to US President Donald Trump's tariff threats on key trading partners after a brief honeymoon. On Saturday, Trump ordered 25% tariffs on goods from Canada and Mexico and a 10% tariff on China,

(Reuters) - U.S. stock index futures tumbled on Monday as fears of a full-blown trade war and its impact on the global economy jolted markets around the world after President Donald Trump levied steep tariffs on Mexico, Canada and China.

Amid warnings of price increases, Canada moved quickly to retaliate, China said it had planned countermeasures and Mexico said it would soon unveil its response.