INCHEON (REUTERS) - Mr Stephen Biegun, the United States special envoy for North Korea, arrived in South Korea on Sunday (Dec 15) as Pyongyang stepped up pressure on Washington to make concessions to revive stalled denuclearisation talks ahead of a year-end deadline.

Mr Biegun's arrival came a day after North Korea said it made another "crucial test" at a rocket launch site to develop a strategic weapon to deter US nuclear threats. Analysts said such tests could help North Korea build more reliable intercontinental ballistic missiles (ICBMs) capable of reaching the US.

Mr Biegun did not make any comments upon arrival at an airport near Seoul on Sunday afternoon.

He plans to meet South Korean President Moon Jae-in on Monday, as part of his three-day stay before leaving for Tokyo to consult with his Japanese counterpart. It is unclear whether he will meet North Korean officials at the inter-Korean border.

Mr Biegun's trip led to speculation he might try to salvage negotiations by reaching out to North Korea, or by publicly sending a message.

North Korean leader Kim Jong Un and US President Donald Trump met three times since last year to negotiate an end to Pyongyang's nuclear and missile programmes, but there has been scant progress.

North Korea has vowed to take an unspecified "new path" if the US fails to address its demands before the end of the year.

Tension has been rising in recent weeks as Pyongyang conducted a series of weapons tests and stepped up criticism of the US, stoking fears the two countries could return to a collision course that they had been on before launching diplomacy last year.