U.S. Deputy Secretary of State William Burns has called for China to boost bilateral cooperation so North Korea can take "meaningful and early steps" to give up its nuclear ambitions, according to a U.S. statement released on Thursday.

Burns was in Beijing as part of his three-nation Asia trip that already took him to Seoul. He is set to leave for Tokyo later Thursday. In Beijing, Burns held talks with Chinese Vice President Li Yuanchao and Vice Foreign Minister Zhang Yesui.

"The Deputy Secretary stressed the importance of close U.S.-China cooperation to obtain meaningful and early steps by North Korea to meet its international obligations and negotiate complete and irreversible denuclearization," the U.S. Embassy in Beijing said in the statement. 

South Korea and the U.S. have been closely watching North Korea amid concerns that Pyongyang could carry out provocations to forge internal unity following the stunning execution of leader Kim Jong-un's uncle, Jang Song-thaek, last month.

In Seoul on Tuesday, Burns said South Korea and the U.S. were both concerned about the recent developments in North Korea that were highlighted by its bloody purge of Jang.

"I think the United States and our friends here share a lot of concerns about the recent behavior of the DPRK (North Korea) leadership, and the dangers of further reckless behavior and provocations in the future," Burns told reporters in Seoul.

Since its third and most powerful nuclear test in February last year, North Korea has repeatedly expressed its willingness to reopen the six-party talks "without preconditions," but Seoul and Washington demand Pyongyang demonstrate its sincerity first by taking steps toward denuclearization.

China has been more accommodating toward North Korea, urging South Korea and the U.S. to lower their bar for Pyongyang to sit down at the negotiating table.

The six-party talks, which involve the two Koreas, the U.S., China, Russia and Japan, have been dormant since late 2008.

(Yonhap)