Testing Trump

America’s enemies can always be counted on to test newly minted US presidents, and seven weeks into Donald Trump’s tenure, they seem to be doing just that — with the stakes sky-high.

Start with North Korea’s firing of four missiles toward Japan last week. Pyongyang said the exercise was practice for attacks on US troops there.

Not alarming enough? How’s this: To counter the North, Washington began shipping a missiledefense system — the Terminal High Altitude Area Defense, or THAAD — to South Korea.

That has infuriated China, which considers the system a threat to it.

“I want to emphasize that we firmly oppose the deployment of THAAD,” huffed Geng Shuang, a spokesman for China’s foreign ministry. He vowed that Beijing would take “necessary measures to defend our security interests.”

As an added twist, a South Korean court removed President Park Geun-hye from office Friday in connection with a corruption scandal, paving the way for a possible shift in US ties to Seoul.

In the Persian Gulf, meanwhile, Iranian vessels taunted a US Navy surveillance ship, veering dangerously within a few hundred yards of it on two separate days.

Tehran also tested a new S-300 air-defense system it got from Russia, Iranian media said, and there were unconfirmed reports the mullahs shot off two ballistic missiles last weekend.

All this was after Iran was “officially put on notice” by the Trump administration, following its launch in January — just nine days after Trump took office — of a medium-range ballistic missile.

The January missile test was also in apparent defiance of a (worthless) UN resolution.

At the time, Trump responded with a stern (you guessed it) tweet: “Iran is playing with fire — they don’t appreciate how ‘kind’ President Obama was to them. Not me!” He followed up by ordering a new round of sanctions. But the latest provocations up the ante. Under Obama, Washington signaled that it would avoid major military conflicts at almost any cost and no matter the provocation. Nations like Russia, China, Syria, Iran and North Korea freely capitalized on that.

Trump was right to portray his predecessor as weak for such a policy. But with the stakes so high — in Asia, the Gulf and elsewhere — the trick is for the new prez to find the right balance between under- and over-reacting.

He’ll need to refrain from making threats he won’t keep, as President Barack Obama did with his red line in Syria — but also not shy away from a truly firm response when necessary.

A wrong move — needless escalations — could prove disastrous. But so, too, could meaningless Obama-style weakness.