U.S. special envoy for the Democratic People's Republic of Korea (DPRK), Stephen Biegun, called on Pyongyang to return its offer of talks, saying Washington remains committed to the nuclear talks with the DPRK. 

Biegun said the United States did not have a "deadline" but wanted to reopen negotiations.

"It is time for us to do our jobs. Let's get this done. We are here, and you know how to reach us," Biegun said.

He made the comments at a joint news conference in Seoul after a meeting with his counterpart Lee Do-hoon, which he described as "productive."

Tension has been rising in recent weeks as Pyongyang has conducted a series of "crucial tests" and traded threats with U.S. President Donald Trump, stoking fears the two countries could return to a collision course that they had been on before launching diplomacy last year.

Referring to the recent tests, Biegun said such actions are "so hostile and negative and so unnecessary."

Washington doesn't have a deadline for nuclear talks and it is willing to discuss "all issues of interest," he added.

The nuclear negotiation between Pyongyang and Washington remain stalled ahead of the year-end deadline set by the DPRK.

On Saturday, the DPRK's Chief of the General Staff Pak Jong Chon said his country was using recent tests to develop new technologies and strategic weapons. In a case of "acute confrontation," the United States "and other hostile forces will spend the year-end in peace only when they hold off any words and deeds rattling us," the country's state media KCNA reported, citing his statement.

"The priceless data, experience and new technologies gained in the recent tests ... will be fully applied to the development of another strategic weapon ... for definitely and reliably restraining and overpowering the nuclear threat of the U.S.," he said.

The test was "successfully conducted at the Sohae Satellite Launching Ground from 22:41 to 22:48 on December 13," the DPRK's National Academy of Defense Science said, without providing further details on the test.

The U.S. diplomat, now the nominee for the deputy secretary of state, arrived in the Republic of Korea (ROK) for a three-day visit on Sunday.

He also met with President Moon Jae-in at the presidential office Blue House and held a luncheon meeting with Unification Minister Kim Yeon-chul, according to Yonhap News Agency.

During the 35-minute session at the Blue House, Moon requested Biegun's continued efforts to move forward the Korean peace process, according to the presidential office. 

(With input from Reuters)

(Cover: The U.S. special envoy for the Democratic People's Republic of Korea (DPRK), Stephen Biegun, arrives at the Incheon International Airport in Incheon, ROK, December 15, 2019. /Reuters Photo)