The United Nations is expected to vote on Thursday on a resolution imposing tougher sanctions on Pyongyang following its third nuclear test.

Analysts urged a restart to negotiations to ease tension on the Korean Peninsula after the Democratic People's Republic of Korea announced on Tuesday it will nullify the Korean War armistice.

During a closed-door meeting in New York on Tuesday, US Ambassador to the UN Susan Rice circulated the draft text of a resolution, proposed by the US, to the other 14 members of the Security Council.

Rice told reporters after the meeting that the DPRK "will be subject to some of the toughest sanctions imposed by the United Nations". She said a vote was likely on Thursday.

Li Baodong, China's permanent representative to the UN, said China will support action by the council as long as it is "proportionate and balanced".

Yu Shaohua, director of the Department for Asia-Pacific Security and Cooperation Studies with the China Institute of International Studies, said the proposed sanctions display the resolve of the international community but they may not deter Pyongyang.

"To some extent, the draft resolution may hinder further nuclear tests, but it will not prompt Pyongyang to abandon its nuclear strategy and it may, in turn, actually stimulate Pyongyang further," Yu said.

The Security Council already imposed sanctions in response to the DPRK's nuclear tests in 2006 and 2009.

The DPRK conducted a nuclear test on Feb 12 despite a Security Council warning and a January resolution expanding sanctions against the country for a rocket launch in December.

Beijing called on Wednesday for calm and restraint in response to Pyongyang's vow to nullify the armistice signed in 1953. No peace treaty has been signed between the DPRK and the Republic of Korea.

"In the long term, we believe that a peace mechanism should replace the armistice," Foreign Ministry spokeswoman Hua Chunying said.

Yu, from the China Institute of International Studies, said the armistice is a "temporary" solution and that Pyongyang's decision to nullify it has shown the urgency to replace it.

The ROK military warned on Wednesday that it will retaliate against the DPRK if it takes any "provocative action", according to Kim Yong-hyun, army major general at the ROK Joint Chiefs of Staff.

A two-month field training exercise called "Foal Eagle" was launched on March 1, with 10,000 US soldiers and 200,000 ROK troops.

A computer-simulated war game called "Key Resolve" will be held between March 11 and 21, involving 10,000 ROK troops and 3,500 US soldiers.

Wang Junsheng, a researcher on East Asian studies with the Chinese Academy of Social Sciences, said the ongoing US-ROK drills are definitely adding to instability.

Despite Seoul's claim that the annual drills are defensive in nature, Pyongyang denounced them as "an irresponsible and dangerous action".

The DPRK decided to halt from Monday the work of its delegation at Panmunjom, where DPRK and ROK delegates meet.

Washington urged Pyongyang to "heed President (Barack) Obama's call to choose the path of peace" and comply with its international obligations, the White House spokesman Jay Carney said.