OTTAWA 鈥� U.S. President Donald Trump is showing no signs of backing away from using tariffs as a negotiating tool, taking to Twitter early Tuesday morning saying "tariffs are the greatest."

In two tweets Trump contradicts his own administration's stated national security justification for steel and aluminum tariffs, saying tariffs are imposed on countries who don't negotiate fair deals with the U.S.

"Countries that have treated us unfairly on trade for years are all coming to Washington to negotiate," The U.S. is also in the middle of a trade dispute with China and is threatening to impose new tariffs on the European auto sector.

"Either a country which has treated the United States unfairly on Trade negotiates a fair deal, or it gets hit with Tariffs. It's as simple as that - and everybody's talking! Remember, we are the 'piggy bank' that鈥檚 being robbed. All will be Great!"

In June when U.S. Secretary of Commerce Wilbur Ross announced the U.S. would be levelling a 25 per cent steel tariff and 10 per cent tariff on aluminum against Canada among other countries, he cited section 232 of the U.S. Trade Expansion Act, which handles trade matters considered a threat to national security.

At the time the U.S. tariffs were announced, various Canadian officials scoffed at the national security assertion, calling it insulting and "difficult to fathom."

These tweets come nearly just about a month after Canada's $16.6 billion in retaliatory tariffs came into effect. Canada's trade response targets American-made steel and aluminum and imports of U.S. goods from chocolate and condiments, to whiskies and motorboats.