Seoul, Oct 4 (IANS): US and North Korean officials were slated to meet on Friday in the Swedish capital of Stockholm, the eve of their formal working-level nuclear talks, after Pyongyang ratcheted up tensions with a test-firing of a new submarine-launched ballistic missile.

The two sides were expected to have "preliminary contact" in Stockholm in the morning before their first official negotiations since the no-deal summit between US President Donald Trump and North Korean leader Kim Jong-un in Hanoi in February, Yonhap News Agency reported.

The exact time and venue for Friday's meeting were yet to be officially announced.

The deputy chiefs of the countries' delegations -- Mark Lambert of the US and Kwon Jong-gun of the North -- were expected to attend the preliminary session.

Top US nuclear envoy, Stephen Biegun, and his counterpart, Kim Myong-gil, could also appear to exchange greetings, observers said.

The talks come after a month-long hiatus caused by gaps in the countries' negotiation positions and tensions triggered by the North's angry reaction to a South Korea-US military exercise in August and its saber-rattling, including the firing of a submarine-launched ballistic missile on Wednesday.

The North's delegation chief Kim Myong-gil voiced optimism in Beijing on Thursday en route to Sweden. His team arrived in the Swedish capital on Thursday afternoon.

"As the US side sent a new signal, I bear high expectations and optimism, and I am also optimistic about the results," Yonhap quoted the official as telling reporters at Beijing International Capital Airport.

Meanwhile, Seoul's foreign ministry has not dispatched any staff to Sweden, though it was keeping a close watch on the resumption of the negotiations between the US and the North.

In a parliamentary audit on Thursday, South Korean Ambassador to the UN Cho Tae-yul made an emphatic call for the North to "change course" and dismiss the idea that time may be on its side.