China is up to its old tricks on trade, but it’s learning the hard way that there’s a new sheriff in town: President Trump.

On Wednesday, Reuters confirmed Team Trump charges that Beijing had reneged on its vows to make numerous key concessions on trade, upending months of talks between Chinese and US officials.

A cable from Beijing on Friday contained “systematic edits to a nearly 150-page draft trade agreement” that “undermined core US demands,” sources told Reuters.

Instead of OKing the deal anyway, Trump fired back, moving to toughen tariffs on Chinese goods: Thursday, the White House filed notice that it would hike fees on $200 billion in imports to 25 percent, up from 10 percent, starting Friday. Trump is also vowing to slap tariffs on more Chinese goods “soon,” absent a deal.

It’s true that such fees are economically harmful; both sides suffer in a trade war, just as in real wars.

But China has operated in bad faith not only in negotiations, but in its actual trade policies, time and again breaking promises to stop stealing intellectual property and trade secrets. Let’s be honest: It was Beijing that started this war.

Yet until Trump, America declined to fight back: “After 20 years of having their way with the US, China still appears to be miscalculating,” noted a private-sector Reuters source briefed on the talks.

In the wake of Trump’s move, Beijing is threatening to retaliate with “necessary countermeasures.” But its options are pretty limited.

Fact is, the US economy is strong, while China’s is slowing. And the US trade deficit with China, $419 billion last year, means Beijing has more to lose from escalations.

You can see why New York’s own Sen. Chuck Schumer is urging the president to “hang tough on China.”

Beijing tried this stunt because it thought it might work, as it has in the past. If a hardball US response is what it takes to force Chinese reforms, so be it. Americans will reap the rewards soon enough.