Four years on from his last visit to the Korean peninsula, at which he expressed his hope for reunification, Pope Francis is about to get another invitation.

But this time from the North.

Kim Jong-un is said to be keen for what would be the first ever trip by a pontiff to the hermit state.

Reuters Correspondent Phil Pullella is at the Vatican.

SOUNDBITE (English) PHIL PULLELLA, REUTERS CORRESPONDENT SAYING: "It's a bit of a long shot right now.

However the Pope has already agreed to go to Japan next year.

So there'd be nothing stopping him going to Japan and then making a stop in South Korea and dipping into North Korea just for a day, I don't think that would be so surprising." North Korea has no formal diplomatic ties with the Vatican.

But the invitation will be delivered by the South Korean president, Moon Jae-in, when he visits the Pope next week.

SOUNDBITE) (Korean) SOUTH KOREA'S PRESIDENTIAL BLUE HOUSE SPOKESMAN, KIM EUI-KEUM, SAYING: "When he meets with Pope Francis, he will convey Chairman Kim Jong-un's message that he will ardently welcome him if he visits Pyongyang." The move by Kim Jong-un is the latest aimed at highlighting growing peace efforts between the two Koreas.

Recently both began dismantling landmines along the border.

U.S. Secretary of State Mike Pompeo announced after weekend talks in Pyongyang that North Korea is now ready to allow international inspectors to visit its nuclear and missile test sites.

The regime is one of the most repressive states in the world, but guarantees freedom of religion in its constitution.

The handful of churches that do exist are tightly controlled.

A mass for peace on the Korean Peninsula is being held at the Vatican next week.

But the Vatican hasn't confirmed if the invitation to Pyongyang will be accepted.