SEOUL (REUTERS) - South Korea's preparations for its first summit with North Korea in more than a decade are in full swing this week, officials said on Sunday (April 22), a day after the North's pledge to end its nuclear tests raised hopes but also scepticism.

North Korea said on Saturday (April 21) it was suspending nuclear and missile tests and scrapping its nuclear test site, and instead pursuing economic growth and peace ahead of planned summits with South Korea and the United States.

The announcement was welcomed by leaders around the world including US President Donald Trump, although he tempered his comments on Sunday, saying the North Korean nuclear crisis is "a long way from conclusion".

Others have expressed doubts about the North's intentions and South Korean President Moon Jae In will be under intense international scrutiny when he meets North Korean leader Kim Jong Un on Friday (April 20).

"North Korea has a long history of raising the issue of denuclearisation and has committed to freeze its nuclear weapons programmes in the past. We all remember how those pledges and commitments went down over past decades," said Professor Nam Sung wook, who specialises in North Korean Studies at Korea University in Seoul.

"Although the North's announcement is quite dramatic, it's natural for the world to be extra sensitive to every word spoken by Kim."

Mr Kim's announcement did not include a commitment to scrap existing nuclear weapons and missiles, and there are doubts he would ever give up the nuclear arsenal his country has been developing for decades.

Mr Kim said North Korea no longer needed to test nuclear bombs or intercontinental ballistic missiles now that his country had the weapons, and he would gear all efforts towards economic development.

Mr Moon, who welcomed Mr Kim's announcement as a "major" step towards denuclearisation, is making the summit his sole focus this week, staying in the presidential Blue House to prepare with no outside engagements, a Blue House official said on Sunday.

South Korea's presidential security service met officials from the military as well as the United Nations Command on Saturday to discuss security at the border truce village of Panmunjom, where the inter-Korean summit will take place, the official said.

For the past few weeks, South Korea has been renovating Peace House, on its side of Panmunjom, to prepare for the summit with Mr Kim, who will be the first North Korean leader to set foot in the South since the 1950-1953 Korean War.

On Monday (April 23), the two Koreas will hold another round of working-level talks at the Tongil Pavilion on the North Korean side of Panmumjom to discuss protocol, security and media coverage of the summit.

Mr Moon now has a direct phone link with Mr Kim on his office desk, instead of having to communicate through a hotline at the Joint Security Area in Panmunjom, which had been the main channel between the two sides over the Winter Olympics in February.

The two leaders are expected to talk over the newly installed phone for the first time this week, before the summit, South Korea said on Friday.

A senior US diplomat for East Asia, Ms Susan Thornton, called North Korea's latest announcement 'a very positive step" as she started a three-day visit to Seoul on Sunday, which will include meetings with South Korea's foreign minister as well as its top nuclear negotiator.

"We are going to be doing a lot of close coordination with South Korea, allies and partners this week," the Yonhap news agency quoted her as saying.

Mr Trump on Saturday called North Korea's offer "very good news". But he dampened his welcome on Sunday, saying on Twitter: "We are a long way from conclusion on North Korea, maybe things will work out, and maybe they won't - only time will tell....But the work I am doing now should have been done a long time ago!"

South Korea said it signified "meaningful"progress that would create good conditions for successful summits with it and later with the United States.

Mr Kim is expected to meet Mr Trump in late May or early June, the first meeting between sitting leaders of the two countries.

US officials say North Korea had in the past repeatedly reneged on denuclearisation agreements, the latest in 2012 when the North launched a long-range rocket after agreeing to a moratorium on missile testing.

Experts also say that North Korea's offer not to test or transfer nuclear weapons appeared a statement of an aim to be a"responsible" nuclear weapons state, rather than an intention to denuclearise.

Dr Cheong Seong Chang, senior research fellow at the Sejong Institute think-tank, said a firm commitment to denuclearise could not be expected before negotiations with the US began.

"Kim cannot give up everything at once. What is clear is that he is showing his earnest willingness to pave the way for smooth negotiations," Dr Cheong said.