Trump needs to speak the blunt truth about North Korea in UN speech

• President Trump needs to be be blunt, not nasty, about North Korea in his U.N. address Tuesday.
• He can't just focus on U.N. finances, he must also point out the U.N.'s moral failings.
• Blunt talk to foreign allies from Trump this year may have soiled his personal reputation, but it seems to have yielded results.

Brendan McDermid | Reuters

President Donald Trump

President Donald Trump seemed to butter up the United Nations Monday with a mostly complimentary set of official remarks ahead of his more anticipated address to the General Assembly on the issue North Korea Tuesday.

And that's when President Trump needs to strip away the flowery talk and be his usual blunt self. The blunter he is, the better chance the world might avoid another war.

Right now, the U.N. and the world needs Donald Trump to be Donald Trump.

That's because it's past time for someone to tell the U.N. General Assembly to its face how its very structure has helped to increase aggression and war-like behavior in the world. When individual members of the Security Council like China and Russia can veto meaningful measures to curb aggression time after time, that aggression is encouraged. And naturally, China and Russia have done just that when it comes to North Korea as they did last week by forcing a watering down of the harshest and probably more effective sanctions against Pyongyang.

Someone has to tell the U.N. that it bears tremendous responsibility for the nightmare that's developing in North Korea and potentially for its neighbors. Donald Trump seems to be the only major world leader willing to say such a thing. President Obama chose to hit other targets, including Donald Trump, in his U.N. speeches. And President George W. Bush spent so many years trying to cultivate and maintain U.N. support for the war in Iraq, that he was hardly in a position to harangue the General Assembly.

President Trump needs to get a critical mass of countries to support the U.S. and Japan in using a boosted military presence to deter Kim Jong Un without firing a shot. He must also call for even harsher sanctions with no interference from China and Russia. And, it's important that he remind world leaders that the alternative is likely a terrible war.

Of course with President Trump, his blunt talk can sometimes be conflated with rude and even crude words. The General Assembly needs to hear an honest and brutal assessment of its inability to truly pressure Kim Jong Un from his homicidal nuclear ambitions. But no good will come of personal insults and trash talk.

President Trump has already proven he can be blunt, but not rude, in his two official trips to Europe. He was plenty blunt to NATO leaders in May when he demanded they do more to pay for the cost of the military alliance. And that seems to have worked to get some member nations to step it up. He also avoided the kind of low-ball antics we often see from him on Twitter at the G20 summit two months later.

But there's something else President Trump needs to avoid. His preliminary remarks Monday focused on waste and mismanagement at the U.N. And as a businessman, President Trump must feel comfortable targeting spending efficiency. But the world is now faced with a threat in North Korea that can't be met with a better balance sheet. President Trump must confront the U.N. with the obligation it has to transcend its moral cowardice. And he must not mince words in doing so.

It's been clear from past foreign trips that President Trump is more focused on results and less about the his personal reputation. In other words, President Trump seems to be OK or at least used to being personally trashed by the media and pundits. He just wants to point to some kind of tangible progress.

He got that with the boosted NATO spending, but now he's reaching for a bigger prize on North Korea. One of the best weapons any U.S. president has at his disposal is clear messaging. This is the time for President Trump to use it and not worry too much about hurting anyone's feelings.

Commentary by Jake Novak, CNBC.com senior columnist. Follow him on Twitter @jakejakeny.

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