As concerns grow over North Korea's military provocations, a range of experts are warning that for various reasons, the U.S. cannot count on China as a reliable partner in defusing the crisis on the Korean Peninsula.

Early Sunday, the U.S. military said it had conducted a successful test THAAD weapon system test over the Pacific Ocean, a response to Pyongyang's latest missile test. That came on the heels of South Korea announcing a new precision ballistic missile it claimed is capable of destroying North Korea's nuclear facilities and tunnel strongholds.

On Friday, The North Korean government test-fired a Hwasong-14 intercontinental ballistic missile into the Sea of Japan. That prompted a furious Twitter tirade from President Donald Trump, who berated China on its inability, or unwillingness, to control its ally.

For its part, China is concerned about the repercussions of North Korea's regime collapsing, including a civil war in an impoverished country with nuclear and chemical weapons. Beijing also is worried a fall of the regime could result in millions of refugees streaming across the border into China, observers say.

"I've been told by senior Chinese officials: 'Look we don't like the status quo but it's certainly a lot better than the alternative,'" said Harry Kazianis, director of defense studies at the Center for the National Interest, a Washington, D.C.-based public policy think tank founded by former President Richard Nixon.

Another reason the administration remains wary of negotiations is previous U.S. attempts at denuclearization have failed, even after substantial assistance to North Korea. In April, Secretary of State Rex Tillerson pointed out the U.S. had provided the North with about $1.3 billion in aid since 1995.

Those factors are playing out against a backdrop of a potential military conflict that grows more acute by the day. Experts now estimate the long-range missile can reach at least half of the continental United States. Yet Joel Wit, a senior fellow at the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies, told CNBC that all was not yet lost.

"I think the 'window of opportunity' is still open for dialogue," said Wit, a co-founder of Washington's 38 North think tank and a former State Department official.

He added that it's time for the Trump administration to sit down and hold "a serious security dialogue" with Pyongyang—and forget about taking the "dead-end" sanctions route.