A Chinese jet fighter last week conducted an “unsafe” intercept of a US spy plane in international airspace over the East China Sea. It’s starting to become a trend — one the Obama administration needs to reverse.

It’s the second such incident in a month — on top of a series of Russian jets repeatedly buzzing US planes and a Navy ship in the Baltic. Beijing and Moscow both seem to think Team Obama can be bullied.

Worse, the Chinese moves directly violate a US-China agreement last September on rules of behavior on air encounters — one that was supposed to reduce tensions.

On top of the real risk of injury from a collision in the latest intercept, China also managed an insult: At the time, Secretary of State John Kerry and Treasury Secretary Jack Lew were in Beijing for an annual meeting.

In both cases, the aggressor is trying to claim territory it doesn’t own.

Beijing is conducting a long-term campaign to seize control of the South China Sea, a plan that also involves the creation of artificial islands that it then packs with military assets.

Moscow, meanwhile, is out to assert dominance in the Baltic — intimidating Norway and Sweden as well as Latvia, Lithuania and Estonia.

Team Obama’s non-response to the Russian provocations probably encouraged China to give it a whirl.

If the White House similarly ignores the latest provocations, expect the likes of Iran or North Korea to be next. And their pilots are a lot less expert — boosting the odds of a fatal collision.

Put it in baseball terms: When the other team starts throwing too many brushback pitches, your players have to respond. And it’s far better to do so early — before you wind up with a bench-clearing brawl.