As tensions mount with North Korea over the country's nuclear ambitions, Department of Homeland Security Secretary John Kelly said the Trump administration is "confident" that China will cooperate with the United States in trying to defuse the situation.

Kelly told Neil Cavuto on Thursday that North Korean dictator Kim Jong Un is "on the march," and it's his clear intent to develop a nuclear missile that can reach the U.S.

"Once that happens, it changes quite a bit of the equation," Kelly said.

"It's just like in the Cold War," he explained. "When a country has a deliverable nuke, that changes how you deal with them."

He said to prevent that from happening, it will be important for China, North Korea's key trading partner, to use sanctions and diplomacy to try and pressure Pyongyang back to the negotiating table.

"I think the administration, the secretary of state and others, are confident that the Chinese will do the responsible thing," Kelly said. "It's not in their interest at all to have a nuclear-capable North Korea. It certainly isn't in their interest to have hostilities break out."

He added that one of China's greatest fears would be a mass migration out of the Korean Peninsula, as they share an 880-mile border with North Korea.

"They obviously have national interests, and it's just not in their national interest in any way to have a nuclear-capable North Korea."

Watch more above.

'People Died for Free Speech!': Pirro Blasts 'Disingenuous' Decision by Berkeley

Coulter: Colleges Like Berkeley Want to 'Squelch' Conservative Speech

ACLU Defends Coulter: 'A Loss For The 1st Amendment'

Trump: I'm 'Absolutely' Considering Breaking Up 'Outrageous' 9th Circuit