US President Donald Trump ramped up his tariff threats to the European Union while saying he would speak with the leaders of Canada and Mexico, as US stock futures sank following a hectic weekend that saw prospects for a trade war turn into reality.

The UK is "out of line" in its trade with the US but the situation can be "worked out", President Donald Trump says. Asked by the BBC if he would target the UK with tariffs while arriving into Maryland from Florida, the US leader says: "We'll see what happens, it'll happen."

Canada, Mexico and China responded to Trump's long-promised tariffs on imports, with Canada immediately retaliating. The EU also weighed in with its reaction.