South Korean President Moon Jae-in speaks during his New Year press conference at the presidential Blue House in Seoul on Tuesday. Photo: AFP

South Korean President Moon Jae-in said on Tuesday it was too early to be pessimistic about stalled denuclearization dialogue between the US and North Korea, and that inter-Korean cooperation could help ease the way for sanctions to be lifted.

Despite hostile rhetoric from Pyongyang, North Korea has not conducted a weapons test nor shut the door to more talks even after Washington ignored its year-end deadline to make concessions, Moon told an annual New Year news conference.

"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.

North Korea said on Saturday that it had received birthday greetings for its leader Kim Jong-un from US President Donald Trump but that their personal rapport is not enough for a return to talks.

Negotiations have been stalled since a daylong meeting in October collapsed, and the US ignored a year-end deadline Kim set for it to soften its stance, calling it "artificial."

The deadlock left South ­Korea increasingly sidelined, with Moon saying in his New Year speech that there is a "desperate need" for practical ways to kick-start cross-border projects blocked by sanctions imposed over Pyongyang's weapons programs.

When asked by Reuters whether South Korea would seek to reopen exchanges with North Korea independently of the US, Moon said there is a need to explore a "new idea" to foster a breakthrough in the stalemate.

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

Moon said there are steps that the two Koreas could take that aren't blocked by the restrictions, including border-­area cooperation and tourism. He also suggested sports exchanges such as fielding combined teams for this year's Summer Olympics in Tokyo, and a joint bid for the 2032 Games.

"If any inter-Korean efforts require an exemption from UN sanctions, we can work to address it," Moon said.