The North went ahead with its second nuclear test in 2009 and declared the six-party talks were eternally dead.

It has been widely believed that the North doesn't like the multilateral denuclearization format due to too many players involved and sometimes irritation coming from Japan, which repeatedly demanded Pyongyang return its kidnapped citizens.

The US appears to have been on the same page as the North at least until last year, when the two countries exchanged ever-intensifying bellicose and vitriolic words. In March last year, US Ambassador to the U.N. Nikki Haley said in an interview with CNN that the US doesn't want to return to the talks.

Things, however, have changed at a breathtaking pace since North Korean leader Kim expressed a willingness in January to send athletes to the Winter Olympics hosted by South Korea.

A series of inter-Korean talks ensued after more than two years of hiatus, and the two Koreas eventually agreed to hold what will be their third summit talks on April 27.

Kim also delivered his invitation through South Korean officials to US President Trump, who accepted it and even proposed to hold their bilateral meeting by the end of May.

Experts say that the North could prefer a multilateral negotiation format to maximize its leverage by enlisting as much support as possible from China and Russia.

"The chances are high for the North to prefer the six-party talks in that the North is worried about the upcoming talks with the US The North might believe that it would be more advantageous to return to the six-party talks than to deal with the US one-on-one," said Woo Jung-yeop, a researcher at the Sejong Institute, a private think tank.

"The North would not prefer to seek a deal through bilateral talks with the US at a time when the US shows no signs of easily making concessions. Should it return to the six-party talks, its belief must be that it could have China, Russia and even South Korea behind its back," he added.

The recent ramped-up diplomatic efforts by the North to reach out to China could be interpreted as a related effort to rally their support and beef up its leverage before the meeting with the US going forward.  The North's possible tilt toward multilateral talks coincides with concerns apparently being shared by China, Russia and Japan wary of being marginalized by the ongoing South Korea and the US-led efforts to handle the nuclear issue.

That could intensify pressure on the US to bring the issue to the multilateral talks going forward.

"The biggest challenge is the US, which has called the denuclearization efforts over the past few decades a failure, which might have referred to the six-party format as well," Woo noted.

"But it could be inevitable for us to return to multilateral negotiations as we will have to deal with the North's security guarantee and other issues regarding the Korean Peninsula," he added.

Cho Sung-ryul, a senior researcher at the Institute for National Security Strategy, echoed the view but noted that the format might not be the same as the long-suspended six-party dialogue.

"Multilateral talks could be held only after the US and North Korea reach a broad-range agreement on denuclearization," he said.

"However, whether that would be six-party or four-party talks involving just the two Koreas, the US and China will remain to be seen."

A government official, meanwhile, said on condition of anonymity that now is the time to focus on the upcoming summits with the North but added the possibility of the six-party talks starting again depends on the outcome of the summits, adding the possibility remains. (Yonhap)