President Donald Trump's "America First" speech to the United Nations didn't put the United States first, former Secretary of State John Kerry said Wednesday — it put "America last and diplomacy last."

"It pushes people away, I mean, this childish kind of, the rhetoric," Kerry told MSNBC's "Morning Joe" program, concerning Trump's strong words against North Korea and its leader, Kim Jong Un. "If name calling was going to solve this problem, Donald Trump would have already solved the problem. So, that's not going to move anybody to do what you have to do."

Further, said Kerry, "you have to ask yourself, is America safer because of 'Rocket Man?' Did we bring anybody to the table as a consequence of that language? You don't give a speech at the United Nations to talk to your base. You have plenty of opportunities to do that. You give a speech at the United Nations to bring people to the table."

The United States needs China to take action, Kerry agreed, as it provides all of North Korea's fuel and financing.

"China would shut North Korea down in one week, two days," said Kerry, but it won't because it says it's afraid of the stability issues that would happen if Kim's regime collapses.

"I think the reason is that they're fearful that, you know, they don't know what comes afterwards, for sure," said Kerry. "But that could, in fact, be guaranteed. I talked to a number of people. There are absolutely ways in which to guarantee a transition here, guarantee that something happens."

Trump, with his blunt speech, lost the opportunity to do what "presidents should do," and bring people together.

"He really should have made it a case for China," said Kerry. "That would have been a legitimate diplomatic gambit, to make the case for why China and how China could do more. That would have been valuable."

Kerry also rejected claims that diplomacy has not worked with North Korea for the past two decades.

"We have less sanctions against North Korea today, which has a nuclear weapon, than we had against Iran, which did not have a nuclear weapon," said Kerry. "How do you figure that out? We brought more pressure to bear on Iran to come to the table and negotiate. When people say we've tried, no, we haven't tried everything. We need to put greater pressure on sanctions because that's the way you exhaust diplomacy."

Further, said Kerry, Trump does not need to "brandish" threats of destroying North Korea to make his point.

"You don't have to brandish that every moment so that it's always the big stick and no talk, literally, softly or otherwise," said Kerry. "You have got to have both. And there's no sense here of diplomatic initiative or effort by them to bring Russia or China to the table to do this."

Kerry also lambasted Trump's call to end the nuclear deal with Iran, saying shredding the deal, which Kerry helped broker, would endanger diplomatic efforts with North Korea.

"What does North Korea think, looking at the way he's talking about shredding a deal that was made?" said Kerry. "If that's the way America behaves in the world, throwing out something that works because you don't like it, but it works, you're actually inviting a much more active path."

Trump's call against the Paris climate agreement is also troublesome, said Kerry.

"Almost 200 nations came together, and all of them agreed simultaneously not to accept the burden imposed by any other country," said Kerry. "Donald Trump has not told the truth to the American people about this. The burden that we've accepted is one we defined. He doesn't have to pull out of Paris. He just has to change the targets."