The dollar firmed on Monday as fresh threats of tariffs from U.S. President Donald Trump dented risk sentiment, casting a shadow over commodities markets and putting pressure on the euro and the Australian and Canadian dollars.

European Union trade ministers will hold an unscheduled video conference on Wednesday to discuss the bloc's response to impending U.S. steel and aluminium tariffs, EU diplomats said on Tuesday. U.S. President Donald Trump signed proclamations late on Monday to raise tariffs on all steel and aluminium imports to 25% without exceptions or exemptions.

The 25% increase on steel and aluminum, along with the taxes in 2018, will make it impossible to export to the United States from Europe. Donald Trump's protectionism is starting to target the European Union.

By Ankur Banerjee and Alun John SINGAPORE/LONDON (Reuters) -Fresh threats of tariffs from U.S. President Donald Trump put pressure on the euro and the Australian and Canadian dollars in early Monday trading,