During his trip to Japan, Vice President Pence promised the U.S. will “not rest” until the Korean peninsula is free of nuclear weapons.

“It is our belief by bringing together the family of nations with diplomatic and economic pressure we have a chance of achieving a freeze on the Korean peninsula,” Pence said Tuesday.

Of those nations, China, which accounts for an estimated 90 percent of North Korea’s trade, is integral to adding pressure on the regime.

“China has real ability to sort of impede the supply chain into North Korea. There are banks, there are businesses. So China really does have tremendous leverage. And the question is, can we bring them to a point where they’ll use it?” said Fran Townsend, CBS News senior national security analyst and former homeland security adviser to President George W. Bush.

Despite President Trump’s optimism that China will use its “extraordinary levers” to pressure North Korea, there have been questions about whether Beijing is serious about working with the U.S. to hinder dictator Kim Jong Un from developing the country’s nuclear program.

Townsend said it’s important to remember China’s strategic interests.

“They don’t want to see chaos in North Korea but they also are not fans of a unified Korean peninsula because what they don’t want to see is U.S. military force on their border in a unified Korea,” Townsend said. “And so we have to understand what each country’s strategic interest is and try to play that to our best advantage.”

While some diplomatic efforts played out openly between Mr. Trump and Chinese President Xi Jinping, Townsend said “we also ought to expect there’s covert and clandestine activity on both sides.”

“We know that North Korea has got cyber ability and we know the United States does as well as electronic warfare capability. And so while we don’t understand the details of that, behind the scenes those sorts of plays are being made,” Townsend said.

Before Mr. Trump softens any trade deals with China, Townsend said the administration needs to see “definite signs” that China is working to mount pressure on the North.

“I think the Chinese have tremendous leverage on trade, diplomacy, sanctions. There’s all sorts of things they can do. We better see that start happening pretty quickly here,” Townsend said.

While North Korea’s latest missile test Sunday failed, Townsend said the regime has made “significant progress” in their program. Last year, North Korea conducted 23 missile tests, according to the Center for Strategic and International Studies. That’s up from four missile tests in 2012.