An historic summit between President Donald Trump and North Korean leader Kim Jong-un kicked off Monday — Tuesday, local time — with mutually respectful words from both leaders.

Trump expressed optimism during a brief joint appearance before reporters in Singapore.

“We had a great discussion, and I think, tremendous success,” he said. “We’ll be tremendously successful … We will have a terrific relationship, I have no doubt.”

Later, when the two leaders sat down with each other and their aides, Trump said, “Working together, we will get it taken care of.”

Kim, meanwhile, also expressed hope.

“Well, it was not easy to get here,” he told reporters through an interpreter. “The past … feathers on our wings, and the old prejudices and practices worked as obstacles on our way forward. But we overcame all of them, and we are here today.”

Responded Trump, “That’s true.”

In some ways, according to experts on Fox News Channel’s “The Ingraham Angle,” the long-term success of U.S. efforts to defang North Korea rests with two countries that are not part of these talks — China and Russia.

“Russia hasn’t had any international clout since it squirmed into Syria when it was invited in by the Obama administration,” Victor Davis Hanson, a senior fellow at the Hoover Institution, told host Laura Ingraham. “Otherwise, it had been out of the Middle East for almost 40 years. So it’s going to try to repeat that, punch above its weight and wiggle in.”

As for China, Hanson added, it is the only reason North Korea has nuclear weapons in the first place.

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Gordon Chang, author of “Nuclear Showdown: North Korea Takes on the World,” said the negotiations with North Korea — despite complaints by critics that it gives Kim a public relations victory and legitimacy — are worthwhile.

“Clearly, we’ve got to talk to the North Koreans,” he said. “It’s much better than the alternative.”

“This moment, I think, is pushing Kim in a direction he may not want to go but, nonetheless, he’s being forced there.”

If Trump succeeds in forging a positive relationship with North Korea, it could have far-reaching geopolitical implications, Chang added.

“That is going to scare both the Chinese and the Russians as well, because it means that we can have one more friend in Asia, and China will have one less friend,” he said.

Several experts who appeared on the show credited the president and his “maximum pressure” campaign of comprehensive sanctions and diplomatic efforts for making the breakthrough.

“This moment, I think, is pushing Kim in a direction he may not want to go but, nonetheless, he’s being forced there,” Chang said.

Harry Kazianis, director of defense studies at the Center for the National Interest, warned the rogue nation has a long history of cheating, lying, and breaking international agreements.

“History screams at us to be cautious,” he said.

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But Kazianis said Trump’s unorthodox approach at has given diplomacy a chance to work.

“He’s willing to take risks. That’s the thing,” he said. “He’s willing to actually put in political capital for this. A lot of other presidents and others wouldn’t do that. Barack Obama wouldn’t do that.”

Michael Pillsbury, director of the Center for Chinese Strategy at the Hudson Institute in Washington, D.C., told Ingraham that the Trump-Kim greeting was a spectacle to behold.

“It’s breathtaking. It is a bit of a cliffhanger,” he said on Monday evening. “We don’t know what’s going to happen at the press conference at 4 a.m. our time … This could be — the president’s re-election is now in the bag.”

PoliZette senior writer Brendan Kirby can be reached at [email protected]. Follow him on Twitter.