U.S. Secretary of State Mike Pompeo said nuclear talks between the U.S. and the Democratic People's Republic of Korea (DPRK) officials starting on Saturday near Stockholm to try to end months of stalemate needed to accomplish a lot of work, but added he was hopeful of progress.

"I'm hopeful that we will (make progress). We came with a set of ideas, we hope the North Koreans came with a good spirit and a willingness to try to move forward and implement what President Trump and Chairman Kim agreed to back in Singapore," he told a news conference from Athens.

Pompeo said that still "a lot of work needs to be done." The fresh nuclear talks were expected to center on how to make substantive progress in the implementation of the landmark agreement that Trump and Kim reached during their first meeting in Singapore in June last year, where they agreed to foster new relations and work towards the denuclearization of the Korean Peninsula.

The meeting at an isolated conference center on the Swedish capital's outskirts will be the first formal working-level talks since U.S. President Donald Trump and DPRK leader Kim Jong Un met in June at the Demilitarized Zone border and agreed to restart negotiations that stalled after a failed second summit in Vietnam in February.

'High expectations'

Early on Saturday, Police closed off the approaches to the complex facing the Baltic Sea on the island of Lidingo, where the delegations led by U.S. Special Representative for DPRK Stephen Biegun and DPRK's Kim Myong Gil met.

Shortly after the morning negotiation session, the DPRK's chief delegate Kim briefly said, "Let's see," in response to a reporter's question of whether he is satisfied with the fresh talks.

Kim on Thursday voiced "high expectations and optimism" over the upcoming working-level denuclearization talks, on his way to Stockholm for the meeting. 

"[We] are heading to working-level negotiations with the U.S.," Kim confirmed to reporters at Beijing International Capital Airport, adding that "as the U.S. side sent a new signal, I bear high expectations and optimism, and I am also optimistic about the results."

The delegation from the DPRK, which is under sanctions banning much of its trade due to its nuclear program, arrived in Sweden on Thursday after Pyongyang unexpectedly said talks would take place on October 5.

On Friday, the countries' deputy delegation chiefs -- Mark Lambert of the U.S. and Kwon Jong Gun of the DPRK -- were said to have had preliminary contact on the outskirts of Stockholm, to discuss administrative issues for the formal resumption of their negotiations.

According to Yonhap, the pre-negotiation session was said to have been "amicable and productive."

Cautious optimism

DPRK First Vice Foreign Minister Choe Son Hui earlier said that the working-level negotiations between Pyongyang and Washington would "accelerate the positive development of the DPRK-U.S. relations."

But uncertainty still shrouds the much-anticipated negotiations given that the DPRK said it had test-fired a new ballistic missile designed for submarine launch only a day after announcing the resumption of talks.

Leaders of both countries face growing incentives to reach a deal but it is unclear whether common ground can be found after months of tension and deadlock over key issues like the scope of Pyongyang's denuclearization, its disarmament method and what rewards it will receive in return.

Earlier on Saturday, newly-appointed Sweden's Foreign Minister Ann Linde had given the European country's first acknowledgment of the working-level talks.

"I am encouraged that U.S. and DPRK working level delegations are currently in Sweden to hold talks. Dialogue needed to reach denuclearization and peaceful solution," Linde said on Twitter.

China also welcomes the resumption of the talks and expects positive outcomes from the dialogue, said Chinese Foreign Ministry on Wednesday.

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China welcomes resumption of DPRK-U.S. talks

DPRK, U.S. to hold working-level talks on October 5