There are clear signs of a "subtle change" in China's approach toward North Korea, which may affect "the calculus" in regional security conditions, a former senior U.S. official said Thursday.

"Yes, there's a subtle shift in Chinese foreign policy...Over the short to medium term, that has the potential to affect the calculus in Northeast Asia," Kurt Campbell said at a forum hosted by the Johns Hopkins School of Advanced International Studies.

"You've seen it at the U.N. (Security Council). We've seen it in our private discussions and you see it in statements in Beijing," he added.

Campbell served as assistant secretary of state for East Asian and Pacific affairs for four years. He left the department in February.

He is one of key architects of the Barack Obama administration's policy of rebalancing diplomatic efforts and military presence toward Asia after a decade of war in Iraq and Afghanistan.

Campbell said North Korean officials are apparently noticing the mood change in Beijing.

"I don't think that subtle shift can be lost on Pyongyang," he said. "They need a close relationship with China for every conceivable reason. It's not in their strategic interest to alienate every country that surrounds them."

He said the U.S. and its regional allies -- South Korea and Japan -- are doing an efficient job in dealing with North Korea's military threats.

They have discerned a gap between the language from Pyongyang and what's going on there actually, he said.

"The most important new ingredient has been a recognition in China that their previous approach to North Korea is not bearing fruit."

Debates are under way in Washington over whether Beijing is actually shifting its policy on Pyongyang, which continues provocative actions, including a nuclear test and long-range rocket launch.

 Obama earlier openly said China is "recalculating" its policy toward the troublesome ally.

"You're starting to see them recalculate and say, 'You know what? This is starting to get out of hand,'" Obama said in a television interview. "And so we may slowly be in a position where we're able to force a recalculation on the part of North Koreans."

But many analysts say there will be no fundamental shift in the foreseeable future, as China needs the survival of the communist ally for many reasons.

Regarding Washington's "pivot" toward Asia, Campbell said the former Bush administration also deserves some credit.

"The truth is that one of the great successes of the Bush administration has been to get Asia more engaged in the Middle East and South Asia," he said.

Meanwhile, former New Mexico Gov. Bill Richardson said North Korea is unlikely to go ahead with "suicidal" attacks.

“There’s been a lot of rhetoric (from North Korea) and not a lot of action, … but I think our response has been appropriate: cool, calm, and at the same time, putting our military resources ready in case there’s an emergency,” he told CNN. “But if they try anything with the United States, it’s suicidal. That’s not going to happen.”

Richardson is known for his personal ties with North Korean officials. He visited Pyongyang in January along with Google Executive Chairman Eric Schmidt. (Yonhap News)