North Korean leader Kim Jong-un has invited Donald Trump to meet him, an unprecedented overture which the US leader has said he will accept.

The shock announcement was made by senior South Korean officials in Washington, who passed on a letter from the North Korean leader.

They said Mr Kim had also agreed to halt nuclear and missile tests and was "committed to denuclearisation".

It appears to be a major breakthrough after months of threats of violence.

However analysts warn that such summits are usually the result of years of careful diplomacy so remain sceptical about what these rapidly arranged talks can achieve.

Mr Trump said the development was "great progress" but that sanctions will remain in place until a firm agreement is reached.

North Korea has not yet issued any official comment on the week's developments.

South Korean National security adviser Chung Eui-yong, speaking outside the White House after the meeting, said: "I told President Trump that at our meeting North Korean leader Kim Jong-un said he's committed to denuclearisation."

He added: "President Trump appreciated the briefing, and said he would meet Kim Jong-un by May to achieve permanent denuclearisation."

How did we reach this point?

North Korea has been isolated on the international stage for decades because of its well-documented human rights abuses and its pursuit of nuclear weapons, in defiance of international laws.

Kim Jong-un had what appeared to be a cordial dinner with South Korean officials this week

It says it needs nuclear weapons and missiles because its survival is under threat. It has carried out six nuclear tests, though it's still unclear whether it could carry out a long-distance nuclear attack.

But South Korea's hosting of the Winter Olympics gave an unexpected window for diplomacy, as rare inter-Korean talks were held to facilitate the North's carefully choreographed attendance.

The South Korean delegation then held landmark talks with Mr Kim in Pyongyang earlier this week.

They returned with a statement saying the North was willing to denuclearise if it felt "it has no reason to retain nukes".

More at http://www.bbc.com/news/world-us-canada-43339901