South Korea and the U.S. remained unwavering in their demands for North Korea’s sincerity toward denuclearization despite the communist state’s peace offensive intensified by a top envoy’s rare news conference at the U.N. over the weekend.

North Korean Ambassador Sin Son-ho in New York on Friday reaffirmed Pyongyang’s offer of senior-level talks with Washington to defuse tension, discuss a peace mechanism to replace the 1953 armistice and resolve the nuclear weapons issue. 

The event came shortly after Kim Kye-gwan, a North Korean vice foreign minister in charge of nuclear bargaining, reiterated the regime’s willingness to engage in “various dialogues including the six-party talks” at a meeting with Yang Jiechi, a Chinese State Councilor in charge of foreign affairs.

But the newest overture was mixed with calls for a lifting of economic sanctions and dismantling of the U.N. Command in the South, which is led by the U.S. that also provides a nuclear umbrella.

North Korea will not give up its “self-defense (nuclear) deterrent” unless the U.S. withdraws its “hostile” policy and nuclear weapons from the peninsula, Sin said.

“The U.N. Command is the U.S. command in essence,” he added in a 10-page statement, calling the unit a “tool of war for aggression which was organized by the U.S.”

Seoul and Washington, however, again dismissed Sin’s remarks as an old tactic that is used chiefly to entice international attention but has little substance.

A government official here said the rare press conference did not show Pyongyang’s sincere attitude toward dialogue. It appeared to be a “face-saving attempt” targeting a South Korea-China summit later this week, where North Korea’s denuclearization will likely top the agenda, the official said.

U.S. State Department spokesperson Patrick Ventrell said Sin’s claims have been repeated by the regime for years, though he had not seen the full context immediately.

“The U.N. command is something that’s been there for many years and will continue to be. … And our sanctions will continue,” he told a daily briefing.

The allies have called on the Kim Jong-un regime to prove its sincerity with preemptive steps toward denuclearization before returning to the negotiating table.

Cho Tae-yong, Seoul’s special representative for Korean Peninsula peace and security affairs and top nuclear negotiator, last week raised the need for “stronger obligations” on the North, before any restart of talks, than those stipulated in its broken agreement with the U.S. on Feb. 29, 2012.

Under the so-called Leap Day Deal, Pyongyang agreed to put a moratorium on its nuclear enrichment program, stop atomic and missile tests and allow IAEA inspections in exchange for 240,000 tons of food aid.

Despite the persistent standoff, brisk diplomacy among the key partners is boosting the prospect for a resumption of a six-nation forum, which was launched in 2003 with the goal of denuclearizing the North but has been dormant since late 2008.

Cho laid out the preconditions after meeting in Washington with Glyn Davies, U.S. Special Representative for North Korea Policy, and Shinsuke Sugiyama, the Japanese Foreign Ministry’s director-general of Asian and Oceanian affairs.

On the way back, Cho visited Beijing for two days from Thursday to hold talks with Wu Dawei, China’s special representative for Korean peninsular affairs. They discussed issues including how to resume the six-party talks, and confirmed that they would not acknowledge North Korea as a nuclear weapons state, diplomats said.

Kim Kye-kwan, the four envoys’ North Korean counterpart at the six-party talks, returned home Saturday after a four-day trip to Beijing which included meetings with Chinese Foreign Minister Wang Yi and Vice Foreign Minister Zhang Yesui, state media said. Kim is also believed to be planning to travel soon to Russia, the other six-party forum member.

A watershed moment may come after the first summit between presidents Park Geun-hye and Xi Jinping on Thursday in Beijing. They are expected to reaffirm their commitment to the denuclearization of the peninsula, but Xi may well persuade Park against “losing a chance at talks” with the northern neighbor.

Further, the ASEAN Regional Forum to be held next week in Brunei could set the stage for dialogue between top diplomats from Seoul, Pyongyang, Washington and other key players, observers say.

“Sin’s news conference and Kim’s trip are an extension of North Korea’s diplomatic offensive ahead of the South Korea-China summit and next month’s 60th anniversary of the armistice agreement,” said Yoo Ho-yeol, a North Korea studies professor at Korea University in Seoul.

Despite Pyongyang’s steadfast nuclear ambitions, he noted as a possible sign of tactical change its recent reference to denuclearization as a “precept” of Kim Il-sung and Kim Jong-il, the two late autocrats and the incumbent ruler’s grandfather and father.

“North Korea seems to be giving weight to its claim for a nuclear state as the groundwork for a new round of negotiations while closely watching other countries’ reactions. Its peace offensive will likely kick into high gear next month,” Yoo told The Korea Herald.

By Shin Hyon-hee (heeshin@heraldcorp.com)