Chinese President Xi Jinping's rare phone call to his South Korean counterpart, Park Geun-hye, underscores growing concerns over North Korea's defiant pursuit of missile and nuclear programs.

It marked the first time that a Chinese leader has held a telephone conversation with a South Korean president over a North Korean nuclear test. No consultations were held between the leaders of the two neighbors when North Korea carried out three previous nuclear tests in 2006, 2009 and 2013.

Park is the first foreign leader whom Xi called over the Jan. 6 nuclear test. Xi has called Park "lao pengyou," meaning old friend in Mandarin Chinese, a sign of personal rapport.

Still, the two leaders did not produce a breakthrough and apparently agreed to disagree on how to deal with North Korea during their 45-minute conversation.

Park asked Xi to cooperate with the U.N. Security Council in adopting strong and effective sanctions on North Korea over its fourth nuclear test last month.

Park made her case for sanctions that are strong and effective enough to make North Korea change its course, saying North Korea's provocations pose threats to peace in Northeast Asia and the world.

"The international community's stern message should quickly lead to action," Cheong Wa Dae, South Korea's presidential office, said of Park's telephone conversation with Xi on Friday night.

Park also "requested China's active cooperation" over the issue, citing China is one of the five permanent veto-wielding members of the Security Council and has influence over North Korea.

The two leaders also exchanged opinions on how to cope with North Korea's planned launch of a long-range missile, the South Korean presidential office said.

China's special envoy, Wu Dawei, returned home empty-handed on Thursday from a three-day trip to Pyongyang. He failed to persuade North Korea to call off its planned rocket launch -- in the latest snub by North Korea.

Still, Xi repeated China's longstanding policy toward North Korea, saying that relevant countries should deal with the situation in a "cool-headed" manner from the perspective of peace and stability on the Korean Peninsula.

"Under any circumstances, China will make efforts to realize Korean-Peninsula denuclearization, safeguard peace and stability on the peninsula and resolve problems through dialogue and negotiations," Xi was quoted as saying.

His comments represent the clearest sign that China will keep status quo policy and that it is opposed to any tougher sanctions on North Korea.

Sue Mi Terry, a former senior CIA analyst on North Korea, said China is still reluctant to join in stronger sanctions for fear that it may lead to destabilization of Kim Jong-un regime.

China voted in favor of tougher sanctions by the Security Council to punish Pyongyang for its third nuclear test in February 2013, though it is widely believed to have been reluctant to enforce tougher measures.

China is North Korea's most important trading partner and a key source of food, arms, and fuel, giving Beijing significant leverage over Pyongyang.

Still, critics say that China is not willing to shift away from its core policy of supporting the status quo, sapping China's influence.

"Fear of instability of the North is still a top concern for the Chinese government," said Terry, now a managing director for business consultancy Bower Group Asia.

China's reluctance could suggest that it is willing to come to the rescue of North Korea, no matter what, as it views Pyongyang as a strategic asset, not a liability.

If China does not join stronger sanctions, it will send the "message to the Kim regime is that North Korea can continue with its provocations because China will never shift from its core North Korea policy -- which is to virtually support it unconditionally," said Terry. (Yonhap)