WASHINGTON — For years, America’s trade agreements have tried to break down economic barriers between nations by removing tariffs and other impediments to cross-border commerce. President Trump’s trade deals have turned that approach on its head.

Mr. Trump’s new trade deal with China promises to lower some of the walls Beijing has erected for foreign companies — including opening its financial markets, streamlining imports of American agriculture and offering greater protection for intellectual property.

But it leaves in place tariffs on the bulk of Chinese imports — more than $360 billion worth of goods. And it requires voluminous Chinese purchases of American products — $200 billion of additional sales over the next two years, according to the Trump administration — a significant shift that experts say moves trade policy away from promoting free markets and back toward an earlier era of managed trade.

Mr. Trump’s newly revised North American trade deal similarly contains provisions that open up markets for dairy, digital services and other industries. But its most transformative changes are to tighten the rules for North American automotive manufacturing to try to spur more production within the continent, a move some Republican lawmakers say will weigh on trade.