Donald Trump. Business Insider composite (Reuters/KCNA/Rick Wilking)

Real-estate tycoon Donald Trump said Wednesday that the US should pressure China into getting North Korea under control.

"It's something I've been talking about for a long time. You have this madman over there who probably would use it," Trump said during an interview on "Fox & Friends."

"And nobody talks to him, other than of course Dennis Rodman," he said. "That's about it."

Trump was referring to North Korea's supreme leader, Kim Jong Un, while addressing North Korea's announcement Tuesday night that it had successfully conducted a hydrogen-bomb test.

Many experts are skeptical that North Korea actually detonated a hydrogen bomb, citing the country's long history of misleading and false claims. But if it did, the incident would represent a significant escalation of the volatile country's nuclear arsenal.

Trump, the Republican presidential front-runner, argued on Fox News that China had the unique ability to curb North Korea's nuclear ambitions. China has long been a benefactor to North Korea and is its primary foreign ally, though the two countries have diverged over Pyongyang's development of nuclear weapons and disruptive regional policies.

"China has … total control over North Korea," Trump said. "And China should solve that problem. And if they don't solve the problem, we should make trade very difficult for China.

"We are holding China up," he added. "They're taking so much money. They're draining our country, and they're toying with us with North Korea. China should do it. They say they can't, they 'don't have that power.' They're toying with our politicians, who don't know what they're doing."

Trump said he would also lean on the US' economic ties and military alliance with South Korea. He lamented that in his view the US got "nothing" despite placing thousands of troops in South Korea.

"I'd get South Korea — that's making a fortune, they're our trading partner, if you want to use the word 'partner,'" Trump said.

He continued: "We get almost nothing for what we do. We defend the world. We defend so many countries. We get nothing. They get everything. We get nothing. South Korea's going to have to start ponying up, OK? And we'll do it in a very nice manner. They'll like us even more than they like us now."

Trump further warned that North Korea was trying to develop the technology to hit the US with one of its nuclear weapons. He said this possibility should demand US action.

"We got to close it down, because he's getting too close to doing something," Trump said. "Right now, he's probably got the weapons, but he doesn't have the transportation system. Once he has the transportation system, he's sick enough to use it. So we better get involved."