Chinese Foreign Minister Yang Jiechi summoned North Korea’s ambassador to China on Tuesday to tell him Beijing was “strongly dissatisfied and resolutely opposed” to North Korea’s nuclear test, the ministry said.

China urged its longtime ally “to honor its commitment to denuclearization and not to take action that may worsen the situation.”

Chinese leaders have spent recent weeks trying strenuously to dissuade Pyongyang from the nuclear test, according to Western diplomats speaking on condition of anonymity. Their failure to do so points to growing exasperation in Beijing with North Korean leader Kim Jong Eun and reflects a deteriorated relationship between the two countries that could have global consequences, the diplomats said.

For years, diplomats and experts have thought that if anyone could persuade North Korea, it was the Chinese. Long seen as a key factor in propping up the regime in Pyongyang, China has come under considerable international pressure to use its influence to push North Korea toward denuclearization and away from provocations.

All the while, China has maintained fairly stalwart support for North Korea — by watering down international sanctions and sending desperately needed aid — even as its leaders tried to convince countries such as the United States that they have limited influence. That assertion seems to have been borne out by Tuesday’s nuclear test.

“The nuclear test of North Korea this time will push China to rethink,” said Zhu Feng, a North Korea expert at Peking University. “In the past, China always thought that the nuclear issue of North Korea could be solved by communication and negotiation. But this time, North Korea showed their determination and hard line to own nuclear weapons, which is not negotiable.”

China — which values stability above all else — is unlikely to abandon North Korea altogether, but diplomats and experts point to clear signs that Beijing could take a much stronger stance against the renegade country this time around.

The most public signs of mounting debate and frustration have been two surprisingly strong editorials in the nationalistic Chinese newspaper Global Times, which warned that China could cut aid to North Korea if it went through with the nuclear test . North Korea, one editorial warned, would “pay a heavy price” for such action.

While not overtly state-run, the Global Times is censored and heavily influenced by the Chinese government, leading many Western diplomats and experts to interpret the editorials and other measures — such as a recent Chinese vote for a U.N. Security Council resolution against North Korea — as precursors to tougher action after a nuclear test.

Another element that may add to stronger Chinese condemnation and reaction to the nuclear test, analysts say, is a sense in Beijing that China’s outgoing leader Hu Jintao gave too much to North Korea without receiving cooperation in return — a perception that China’s new leader Xi Jinping may look to correct.

“Although one single nuclear test won’t change the relationship between China and North Korea, the changing process has begun,” said Peking University expert Zhu.

“China’s influence over North Korea decreased because it never implemented any unilateral economic sanctions toward North Korea,” said Zhu, offering a view that has become increasingly common in Beijing. “But I doubt even now that China will announce any unilateral sanction toward North Korea.”

There is also danger that North Korea could grow frustrated with Beijing, said Stephanie Kleine-Ahlbrandt, North East Asia director for the International Crisis Group in Beijing. Kim Jung Eun has yet to visit Beijing since becoming leader of his country. Several attempts by China in the past year to send high-level diplomats to Pyongyang appear to have been given the cold shoulder.

“North Korean resentment of China is at a high now,” Kleine-Ahlbrandt said . “The more they depend on China, the more they resent China. The relationship frankly has been a challenge, especially the past year.”

But the best indication of where North Korea and China — North Korea’s most important relationship with the outside world — are ultimately headed won’t be evident until the U.N. Security Council meetings scheduled for this week, say international experts. They are eager to see how far China is willing to go in joining international condemnation of the test and in supporting stricter sanctions.

Zhang Jie in Beijing contributed to this report.