BEIJING — The theory goes like this: Parts of the US government — nobody is quite sure which parts, but parts nonetheless — have no desire for North Korea to give up its nuclear weapons program. They love North Korea’s nuclear weapons, the theory goes, because it provides a convenient excuse for the US to keep military assets in South Korea and Japan.

This might sound crazy if you’re in the US. US leaders from Bill Clinton, to George W. Bush, to Barack Obama have spent decades trying to persuade North Korea to give up its banned nuclear and ballistic missiles programs through endless rounds of talks and sanctions.

But in China, where suspicions of US motives in the region run deep and there is little faith in government transparency, the theory has been judged plausible by everyone from casual news consumers to journalists and academics with influence on North Korea policy.

“The US is using North Korea’s nuclear weapons as an excuse,” Lu Chao, director of the Border Study Institute at the Liaoning Academy of Social Sciences, a government think tank, told BuzzFeed News. “The real goal is strategic — it’s to reshape the balance of power in northeast Asia. That’s what I believe.”

That lack of trust underscores a key challenge for a new administration as it contends with an increasingly confident and aggressive North Korea. President Donald Trump has made clear he believes China has the power to shape North Korea’s behavior. But the festering mistrust between Washington and Beijing may prove to be a major obstacle to the two countries effectively working together to pressure Pyongyang.

The theory that the US is secretly rooting for Pyongyang’s nuclear program isn’t a mainstream viewpoint, according to Chinese journalists and academics. But the belief that the US approaches North Korea policy with a hidden motive — the containment of China — has become widely accepted in Chinese policymaking circles.

“Of course there is a lack of trust,” said Zhang Liangui, a professor at the Central Party School and one of the country’s top North Korea experts. “China suspects that the US has ulterior motives when it comes to North Korea.”

It isn’t just China coming up with theories that leave the other side of the negotiating table baffled. The Chinese thinkers interviewed for this story pointed out that the US has its own theories about China’s point of view on North Korea that appear ridiculous to them. For instance, most Chinese scholars believe the collapse of the North Korean regime is extremely unlikely, and China bristles at the suggestion by many in the US — including Trump — that China could engineer the collapse of the North Korean government as easily as flicking a light switch.

Over the past few weeks, though, the divide has taken on a heightened importance. Chinese questions about the motives of the US have resurfaced as the US deployed parts of an advanced missile defense system called the Terminal High-Altitude Area Defense (THAAD) to South Korea, a move that has incensed China. Beijing sees THAAD as an escalatory move by the US that does little to curb the North Korean nuclear program — but many Chinese policymakers think it could potentially help contain China.