North Korean leader Kim Jong Un has reopened a key cross-border communication channel with South Korea for the first time in nearly two years as the rivals explore the possibility of talks after months of acrimony.

Mr Kim’s announcement, read by a senior official on state TV, followed a South Korean offer on Tuesday of high-level talks to find ways to co-operate on next month’s Winter Olympics in the South and discuss other inter-Korean issues.

Ri Son Gwon, chairman of the state-run Committee for Peaceful Reunification, said Mr Kim welcomed South Korea’s overture and had ordered officials to reopen a communication channel at the border village of Panmunjom.

South Korea quickly welcomed the decision and later confirmed the two Koreas had started preliminary contacts on the channel.

A South Korean government official checks the direct communications hotline to talk with the North Korean side at the border village of Panmunjom in Paju, South Korea (Yonhap via AP)A South Korean government official checks the direct communications hotline to talk with the North Korean side at the border village of Panmunjom in Paju, South Korea (Yonhap via AP)

But even among the sudden signs of easing animosity, Donald Trump threatened Mr Kim with nuclear war.

In his new year address on Monday, Mr Kim said he was willing to send a delegation to the Winter Olympics, but he also said he has a “nuclear button” on his desk and that all US territory is within striking distance of his nuclear weapons.

This prompted the US president to boast of a bigger and more powerful “nuclear button” than Mr Kim’s.

The two leaders exchanged crude insults last year after the UN imposed new sanctions over the North’s sixth and most powerful nuclear test explosion and a series of intercontinental ballistic launches.

The recent softening of contact between the rival Koreas may show a shared interest in improved ties, but there is no guarantee tensions will ease.

There have been repeated attempts in recent years by the rivals to talk, but the efforts often end in recrimination and stalemate.

Outside critics say Mr Kim may be trying to use better ties with South Korea as a way to weaken the alliance between Washington and Seoul as Pyongyang grapples with toughened international sanctions over its nuclear and missile programmes.

Since taking office last May, South Korea’s liberal President Moon Jae-in has pushed hard to improve ties and resume stalled co-operation projects with North Korea. Pyongyang had not responded to his outreach until Mr Kim’s new year address.

Relations between the Koreas soured under Mr Moon’s conservative predecessors, who responded to the North’s expanding nuclear programme with hardline measures.

All major rapprochement projects were put on hold one by one, and the Panmunjom communication channel has been suspended since February 2016.

Mr Moon has pushed for more pressure and sanctions on North Korea, but he still favours dialogue as a way to resolve the nuclear stand-off.

The Trump administration says all options are on the table, including military measures against the North, but Mr Moon has repeatedly said he opposes any war on the Korean peninsula.

Some observers believe these differences may have led Mr Kim to think he could drive a wedge between Seoul and Washington as a way to weaken their alliance and international sanctions.

Talks could provide a temporary thaw in strained inter-Korean ties, but conservative critics worry that they may only earn the North time to perfect its nuclear weapons.

After the Olympics, inter-Korean ties could become frosty again because the North has made it clear it has no intention of accepting international calls for nuclear disarmament and instead wants to bolster its weapons arsenal in the face of what it considers increasing US threats.