Seoul, South Korea (CNN) North Korea says its quest for nuclear weapons is "complete" and it "no longer needs" to test its weapons capability, a significant development ahead of diplomatic engagement with South Korea and the United States.

North Korean leader Kim Jong Un said Saturday that "under the proven condition of complete nuclear weapons, we no longer need any nuclear tests, mid-range and intercontinental ballistic rocket tests, and that the nuclear test site in northern area has also completed its mission," as quoted by the state-run Korean Central News Agency, or KCNA.

The announcement appears to signify a remarkable change in policy for Kim, following a relentless pursuit of nuclear and ballistic weapons as a means to ensure his regime's survival -- although some analysts remain skeptical, pointing out that Kim hasn't tested a missile since November.

The news comes six days before a meeting between Kim and South Korean President Moon Jae-in, a precursor to a much-anticipated planned encounter between Kim and President Donald Trump expected to take place in late May or early June.

It also comes weeks after the North Korean leader met Chinese President Xi Jinping on his first official trip outside his country.

The United States and South Korea welcomed the development, which they said was a sign of progress and a promising start to upcoming talks.

"North Korea has agreed to suspend all Nuclear Tests and close up a major test site," Trump tweeted. "This is very good news for North Korea and the World - big progress! Look forward to our Summit."

North Korea has agreed to suspend all Nuclear Tests and close up a major test site. This is very good news for North Korea and the World - big progress! Look forward to our Summit. — Donald J. Trump (@realDonaldTrump) April 20, 2018

Seoul offered similar praise, with South Korean presidential official Yoon Young-chan telling journalists the news represented "meaningful progress for denuclearization of the Korean Peninsula," and said it would contribute to a "positive environment" for the upcoming talks.

A new chapter for North Korea?

A North Korea source told CNN that Kim has finally decided to open up a new chapter for his nation. Kim has committed himself to the path of denuclearization and will now focus solely on economic growth and improving the national economy, the source said.

The North Korean leader has realized the best path forward is to normalize relations with other countries, the source added. He is finally being recognized by the international community, and this is a historic, timely opportunity, the source said.

Analysis CNN's Will Ripley, who has reported from North Korea 17 times, says that Kim "is trying to send the world a positive signal ahead of a potentially monumental summit with President Donald Trump. But the steps he is taking at this point are largely symbolic. Operations at missile and nuclear testing sites could easily be resumed, since North Korea has not agreed to destroy weapons or dismantle key facilities. Furthermore, nuclear weapons -- and the materials to make them -- are undoubtedly hidden at secret sites throughout North Korea that are unknown to the US and its allies. Taking more substantive steps towards denuclearization will come at a high price, far higher than 1994's Agreed Framework that promised North Korean denuclearization in exchange for light water reactors (that were never built) and heavy fuel shipments (that were often late). This announcement indicates a willingness by Kim to explore denuclearization in exchange for better economic conditions. But it won't be easy to convince him to give up the missile program that has arguably gotten him to this point, unless there are substantial incentives to do so."

Japanese Prime Minister Shinzo Abe cautiously welcomed the development. "The only thing that is important is whether or not it will lead to the completely verified and irreversible abolition of nuclear and missiles," Abe told reporters. "We would like to keep a close eye on it."

Japanese Defense Minister Itsunori Onodera went one step further, saying that the suspension of nuclear and missile tests was "insufficient" and "not satisfactory," as it did not mention Pyongyang's short- and midrange capabilities -- the missiles that can reach Japan.

Beijing welcomed the news and pledged to play a "positive" role in bringing lasting peace to the peninsula.

"Achieving denuclearization and sustainable peace in the region is in the interest of people on the peninsula and in the region, and meets the shared expectation of the international community," Chinese Foreign Ministry spokesman Lu Kang said.

UN Secretary-General Antonio Guterres called North Korea's decision a "positive step forward." In a statement through his spokesman, he also wished the leaders of the two Koreas "every success in their courageous and important task of resuming sincere dialogue leading to sustainable peace on the Korean Peninsula" ahead of next week's summit.

European Union foreign policy chief Federica Mogherini described the announcement as "a positive, long sought-after step on the path that has now (led) to the country's complete, verifiable and irreversible denuclearization" and adherence to international obligations.

The EU will "continue to support a negotiated solution in any way possible," she said, while also maintaining strong pressure on North Korea through sanctions.

Analysts stressed caution over Kim's words, noting that Pyongyang was likely to be seeking something in return.

"The announcement is significant, but you know, whether North Korea is truly serious remains to be seen," said Sue Mi Terry, a former CIA North Korea analyst.

"They might be looking for freeze-for-freeze deals. They are looking for sanctions relief. So what are we going to give for this freezing of tests?"

Josh Pollack, senior research associate at the Middlebury Institute of International Studies at Monterey, said the news was Kim's way of announcing his country is a fully paid-up member of the nuclear club.

"They have wanted to be seen as an arrived nuclear power for a while and one thing that the other nuclear powers don't do is test, with the exception of India and Pakistan, no one has done it since 1996, so it's a sign of immaturity to test and they're saying: 'We're technically mature now, so we don't need to (test) anymore.'

"They're not giving anything up, they're keeping (their weapons) and that's the message. It was wrapped in this seeming concession, but it's not really a concession. (If) they can decide to test after all, they can just start doing it again."

6-point list on nuclear objectives

The change in North Korea's policy was announced via state news agency KCNA. It published a six-point list that emphasized the country had achieved its nuclear objectives.

• "We declare solemnly that we faithfully realized the nuclear weaponization" -- The first point says the tests were carried out under its " byungjin " policy, a twofold strategy of investing in the economy and the nuclear program. Tests were carried out in sequential order to achieve the country's aim.

• "The nuclear test site in northern area will be discarded" -- KCNA said as of Saturday that North Korea will no longer conduct nuclear or intercontinental ballistic missile tests, and to "ensure transparency" the test site would be closed.

• "(It's an) important process for global nuclear disarmament" -- North Korea says it'll work with the international community to halt nuclear testing worldwide.

• "We will never use nuclear weapons unless there is a nuclear threat or nuclear provocation to our country" -- Nor will North Korea transfer nuclear weapons and technology, KCNA said.

• There's a commitment to "dramatically raise people's lives" -- Development of a "strong socialist economy" will become a priority for the country.

• North Korea "will intensify close ties and dialogue" -- The country says it'll improve relations with neighboring countries and the international community to promote peace on the Korean Peninsula and beyond.

6 nuclear tests

North Korea conducted its sixth nuclear test in September deep underground at the Punggye-ri nuclear test site in North Hamgyong province. The explosion created a magnitude 6.3 tremor, making it the most powerful weapon Pyongyang has ever tested.

​North Korea has worked for years to miniaturize a nuclear warhead so it can be fitted atop a long-range missile and survive the heat-intensive process of re-entering the Earth's atmosphere.

Last year, Pyongyang tested a new intercontinental ballistic missile it said could reach the US mainland, raising the prospect that Kim could follow through on his threat to target the United States.

The decision to halt nuclear and missile testing comes nearly a week before the leaders of South and North Korea are due to meet in the Demilitarized Zone between the two countries.

The planned encounter follows months of warming relations since Kim held out an olive branch in his New Year's Day speech.

The two countries started talking again for the first time in two years via a special phone line, and those talks led to North Korea's participation in South Korea's Winter Olympics.

Kim extended an invitation to South Korea's leader to go to Pyongyang, and the two agreed to meet Friday at the heavily fortified DMZ. A hotline between the two capitals has been reconnected ahead of the talks.

CORRECTION: This article has been updated to correctly show the status of nuclear weapons testing. With the exception of India and Pakistan, no nation has tested a nuclear weapon since 1996, according to analyst Josh Pollack.