Washington (CNN) President Donald Trump dug into his protectionist trade position on Friday, arguing that trade wars can be good and vowing to slap reciprocal tariffs on any goods even as his actions rattle markets and anger US allies.

The tweets were a retrenchment of long-standing views on trade that Trump hopes will rally his base and spur job creation in the United States. But the views have worried investors -- markets opened sharply lower -- and even some of Trump's own advisers have resisted the harsh new actions.

"When a country (USA) is losing many billions of dollars on trade with virtually every country it does business with, trade wars are good, and easy to win," Trump wrote on Twitter early Friday.

When a country (USA) is losing many billions of dollars on trade with virtually every country it does business with, trade wars are good, and easy to win. Example, when we are down $100 billion with a certain country and they get cute, don't trade anymore-we win big. It's easy! — Donald J. Trump (@realDonaldTrump) March 2, 2018

He added, "Example, when we are down $100 billion with a certain country and they get cute, don't trade anymore-we win big. It's easy!"

Later Friday, he tweeted: "We must protect our country and our workers. Our steel industry is in bad shape. IF YOU DON'T HAVE STEEL, YOU DON'T HAVE A COUNTRY!"

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