While the U.S. is pushing for "the strongest possible" sanctions against North Korea after that country's sixth and largest nuclear test Sunday, North Korea is reportedly moving what appears to be another intercontinental ballistic missile (ICBM) toward a launch pad.

As tensions between U.S. allies and the North continue to rise, retired Adm. James "Sandy" Winnefeld, who was vice chairman of the Joint Chiefs of Staff from 2011 and 2015, said "the last thing" Kim wants "is a war right now."

"I don't think that Americans should be panicking over this at all," said Winnefeld, a CBS News military and homeland security analyst. "We have a very good nuclear deterrent. Even though Kim Jong Un will probably never give up his nuclear weapons, he will not use them as long as his regime is not perceived to be at risk. So I would encourage everybody take a deep breath and let's let this play its course."

Retired Adm. James "Sandy" Winnefeld CBS News

Winnefeld, who said North Korea's weapons capabilities are "not all that much of a surprise," said Kim has been "acting fairly rationally."

"The reason he would never use them is it would be, as [Defense Secretary] Jim Mattis pointed out over the weekend in a very calm and measured manner – it would be suicide if he were to ever use a nuclear weapon because he would face a very strong, retaliatory response," Winnefeld said.

President Trump has called for China's help to pressure North Korea to negotiate – and China has urged the regime to halt its missile tests – but some like Winnefeld believe China could play a bigger role in imposing sanctions. However, Winnefeld said the Trump administration should have "quiet diplomacy with China right now."

"[China has] a party congress coming up in mid-October. The worst thing we could do right now is put them on the spot publicly," Winnefeld said. "But I think we need to be very firm with them privately and get them to back sanctions not only publicly in the U.N. Security Council but to actually put the teeth in them on their border."

Getting China to do that, however, may be a challenge. According to East Asia expert Richard McGregor, who's out with a new book called "Asia's Reckoning: China, Japan, and the Fate of U.S. Power in the Pacific Century," sanctions could backfire on China.

"The problem with China is – China has an enormous economic leverage over North Korea, that is the kind of leverage if they use, it could come back against them," McGregor said. "If North Korea collapsed, if North Korea fell into the arms of South Korea, then China would have a U.S. ally on its border. And China's made the choice so far, no matter how crazy North Korea has got, keeping them there is better than having them as part of a U.S. ally."