US President Donald Trump is not backing down from the tough line he has taken on trade, the White House's top economic adviser said on Wednesday, setting the stage for a showdown with top allies at this week's G7 summit in Canada.

The meeting in Quebec, will be the first chance G7 leaders have had to confront Trump in person since US tariffs on steel and aluminum imports from Canada, Mexico and the EU were imposed last week. That move unleashed fury in the Group of Seven industrialised nations and prompted quick retaliation from Canada and Mexico and a promise from the EU to do so as well, unnerving investors who fear a trade war that could derail the global economy.