SEOUL, South Korea -- The leaders of China and South Korea agreed at a summit meeting in Beijing on Thursday to work together to resume six-nation talks aimed at ending North Korea's nuclear weapons programs, calling them a "serious threat" to stability in East Asia.
A joint statement issued after the meeting between the leaders, President Xi Jinping of China and President Park Geun-hye of South Korea, also said they had agreed on the importance of faithfully carrying out United Nations Security Council resolutions that called for sanctions against North Korea, as well as a multilateral agreement in 2005 under which the North was obliged to give up its nuclear weapons programs in return for economic and diplomatic benefits.
Although South Korea and China have separately declared their opposition to North Korea's nuclear weapons programs many times, their two leaders speaking in one voice during a rare joint press appearance carried some diplomatic symbolism: South Korea is the North's archrival, while China is its biggest ally. "Both sides confirmed that denuclearizing the Korean Peninsula and keeping peace and stability there were in their common interest, and they agreed to make joint efforts to that end," the statement said.
Although the statement said Ms. Park and Mr. Xi agreed to take "active efforts to create positive circumstances for the resumption of the six-party talks," it did not divulge any details.
"We hope all sides seize this opportunity and work together to return to the six-party talks at an early date," Mr. Xi said during his meeting with Ms. Park, according to a statement from the Chinese Foreign Ministry.
For her part, Ms. Park said she and Mr. Xi agreed that the North's possession of nuclear weapons could not be tolerated "under any circumstances."
The six-nation talks, of which China is the host, have been stalled since 2008. North Korea has since conducted its second and third nuclear tests and launched long-range rockets that were seen as a cover for testing technology for intercontinental ballistic missiles. Besides China and South Korea, the nations involved in the talks are the United States, North Korea, Japan and Russia.
Although China endorsed United Nations sanctions against North Korea after its recent nuclear tests, it has championed the talks as a key effort to end the North Korean nuclear crisis. In contrast, South Korea and the United States, its ally, have grown increasingly reluctant to engage North Korea with yet another round of negotiations unless the North shows signs that it is serious about giving up its nuclear weapons.
Both have said they opposed "talks for talks' sake" with North Korea. Attempts to restart government dialogue between North and South Korea collapsed in mutual recriminations this month, and their relations remain chilly.
Ms. Park arrived in Beijing on Thursday for a four-day visit that included her first formal meetings with Mr. Xi and Prime Minister Li Keqiang since she was elected the first female president of her country in December. She has vowed to enlist China's help in her drive to end North Korea's nuclear programs and its provocative behavior.
Although China is North Korea's biggest source of diplomatic and economic support, their trade is a fraction of the mutual trade between China and South Korea. Beijing has shown signs of frustration with its longstanding Communist ally in Pyongyang, especially after the North's long-range rocket launching in December and its third nuclear test in February.
It has since supported tightening United Nations sanctions, cracked down on North Korean banking activity and pressed Pyongyang to agree to return to disarmament talks when its envoy visited Beijing last month. Kim Kye-gwan, North Korea's veteran negotiator on nuclear issues, told Zhang Yesui, the Chinese vice foreign minister, during discussions last week that it was ready to join any form of meeting, including the stalled six-party talks, according to the Chinese Foreign Ministry.
The friendly meeting between the Chinese and South Korean leaders came as the United States escalated its sanctions on North Korea, blacklisting Daedong Credit Bank in the North, a related company and a North Korean nuclear research official. The action, announced by the Treasury Department, was part of what it called "our ongoing efforts to disrupt North Korean financial networks supporting the regime's illicit ballistic missile and weapons of mass destruction programs and proliferation activities."
Under the American sanctions, dealings with blacklisted entities and individuals are prohibited, and any assets they may have under American jurisdiction can be seized.
David S. Cohen, the Treasury under secretary in charge of American financial sanctions, said the timing of the action was purely coincidental to the meeting in Beijing. "We are committed to increasing the sanctions pressure on North Korea until it complies with its international obligations," he told reporters in a telephone news conference.
The United States has been far more aggressive than China in its financial sanctions on North Korea. But doubts remain that Beijing will apply the kind of economic pressure against North Korea that Washington and Seoul want. A common view among regional analysts is that although it is unhappy with the North's nuclear ambition, Beijing will keep the North as a buffer against the United States and South Korea, rather than pushing the North Korean government too hard and risking instability on its border.
Ms. Park is scheduled to continue her discussions with senior Chinese leaders on Friday, meeting with Mr. Li and Zhang Dejiang, leader of China's legislature and a graduate of Kim Il-sung University in North Korea. She is also scheduled to deliver a speech at least partly in Chinese to students at Tsinghua University in Beijing this week.
Ms. Park also plans to become the first South Korean president to visit the city of Xi'an, in Mr. Xi's home province, Shaanxi, where many South Korean companies have invested.
Bree Feng contributed reporting from Beijing, and Rick Gladstone from New York.
This article originally appeared in The New York Times.