South Korean President Moon Jae-in said Tuesday that North Korea could still be open to negotiations over its nuclear program with the United States, despite recent threats from Pyongyang.

“North Korea made clear that the door to dialogue is not closed though there’s a premise that they can come back to talks only when their demands are accepted,” Moon said. 

Moon, considered a mediator between the U.S. and North Korea, also referenced the role Kim's recent birthday may have played in restarting talks.

"Many were worried about a possible military provocation ahead of Chairman Kim Jong Un's birthday, but instead, there was a congratulatory message from President Trump," Moon said.

North Korea has recently said that it felt “deceived” by the U.S. over the stalled negotiations, while U.S. national security adviser Robert O’Brien encouraged Pyongyang to come back to the negotiating table. 

The last time U.S. and North Korean negotiators met was in early October, but talks fell through on the first day of meetings. The U.S. wants North Korea to pursue a path to denuclearization, while North Korea wants sanctions on its economy to be lifted. 

Moon told Reuters that if North Korea and South Korea work more together, it could also facilitate the U.S.-North Korea dialogue. 

“If we expand inter-Korean cooperation as much as possible, it will be able to not only expedite North Korea-U.S. dialogue, but also fetch international support for partial lifting or exemptions of sanctions if necessary,” he said.

One idea could be allowing South Koreans to visit the North for tourism purposes, which would help the North Korean economy. The North Korean tourism industry is exempt from international sanctions, with the country opening up new resorts in 2019. 

North Korea had been angered last year by planned U.S.-South Korea joint military exercises, which Pyongyang views as the preparation for an invasion. The Pentagon had decided to postpone the exercises but North Korea wants the military drills to be canceled completely. 

North Korea may test new weapons this year, in order to provoke Washington, but these actions would also threaten the country’s East Asian neighbors, such as Japan and South Korea. North Korea had threatened the U.S. with a “Christmas gift” during the recent holiday season, which some analysts believe to be an intercontinental ballistic missile test, but no tests ended up taking place. 

North Korea and South Korea are still at war with each other, as the Korean War ended in 1953 with a truce, not a peace treaty.