The United States expects China to use its leverage and leadership to persuade Pyongyang to get back to substantive negotiations over its denuclearization, a leading US nuclear envoy said on Jan 30.

"China has a very special relationship with the Democratic People's Republic of Korea and there is no change in China's commitment to denuclearization of the Korean peninsula," said Sung Kim, US Special Representative for DPRK Policy, in Beijing.

Kim said the US will continue to have effective cooperation and coordination with China on all aspects of the country's DPRK policy, including sanctions enforcement.

"China should well play a leadership role in the six-party process to persuade Pyongyang to come back to critical and serious negotiations, to achieve substantive results," Kim told reporters before concluding his Asia trip, which took him to Japan and China. It had been six weeks since Kim's last visit to Beijing.

Kim's remarks came after his colleague Wendy Sherman, US Undersecretary of State for Political Affairs, lauded Beijing days ago for being helpful recently in making it clear that "denuclearization is the priority for Pyongyang's relationship with China, with the region and with the world".

On Jan 30, Chinese Foreign Ministry Spokeswoman Hua Chunying also urged all relevant parties to create conditions for a "flexible and practical attitude" for an early resumption of the Six-Party Talks.

The Six-Party Talks, which involve China, the US, Russia, Japan, the Republic of Korea and the DPRK, were initiated in Beijing in August 2003 but have been stalled since December 2008.

The US recently dismissed an unconditional resumption of the Six-Party Talks suggested by the DPRK, urging Pyongyang to abide by its denuclearization commitment.

"The question is not what we are willing to do. The question is that North Korea is not ready for any serious and productive talks on the nuclear issue," Kim said.

Wang Junsheng, a researcher on East Asian studies with the Chinese Academy of Social Sciences, said it is quite likely that the Six-Party Talks will resume this year under China's bridge-building efforts, given that all parties recognize the framework as the best channel for communication.

"However, it hinges on whether Pyongyang will observe former consensus on its denuclearization obligations with sincerity," Wang said. "The talks cannot resume ‘unconditionally'."

The envoy also emphasized Russia's "clear and strong" denuclearization position, when asked about DPRK leader Kim Jong-un's reportedly possible visit to Moscow in May to attend celebrations of the Soviet victory against Germany in WWII. It would be his first foreign visit since taking power in 2011.

"If it happens, the multilateral occasion will become a great opportunity for Pyongyang to improve its global image and ties with regional stakeholders," Wang said.

In another development, the US imposed sanctions against the DPRK government early last month for what it called Pyongyang's "numerous provocations", particularly the "destructive and unprecedented" cyber-attack on Sony Pictures Entertainment over a comedy film, The Interview, which depicts an assassination attempt on the DPRK leader. Pyongyang has denied involvement in the incident.

Douglas Paal, vice-president for studies at the Carnegie Endowment for International Peace, said the cyber-security issue, if properly addressed, however, could become the basis for relevant sides to re-approach each other and have a positive conversation.

Chen Weihua in Washington contributed to the story.