SEOUL, South Korea -- North Korea announced that it will suspend nuclear tests and intercontinental ballistic missile launches ahead of its summits with Seoul and Washington, but stopped short of suggesting it has any intention of giving up its hard-won nuclear arsenal. The announcement, which sets the table for further negotiations when the summits begin, was made by leader Kim Jong Un at a meeting of the North Korean ruling party's Central Committee on Friday. It was reported by the North's state-run media early Saturday.

Kim justified the suspension to his party by saying the situation around North Korea has been rapidly changing "in favor of the Korean revolution" since he announced last year that his country had completed its nuclear forces. He said North Korea has reached the level where it no longer needs underground testing or test-launching of ICBMs, and added that it would close its nuclear testing facility at Punggye-ri, which was already believed to have been rendered unusable due to tunnel collapses after the North's test of its most powerful bomb to date last year.

The announcement is Kim's opening gambit to set the tone for summit talks with South Korean President Moon Jae-in, set for next Friday, and President Trump, expected in late May or early June.

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Mr. Trump, who is at his Mar-a-Lago resort in Florida, was quick to describe the development as "progress." He almost immediately responded with a tweet, saying, "This is very good news for North Korea and the World." He added that he's looking forward to his summit with Kim.

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

A message from Kim Jong Un: “North Korea will stop nuclear tests and launches of intercontinental ballistic missiles.”

Also will “Shut down a nuclear test site in the country’s Northern Side to prove the vow to suspend nuclear tests.” Progress being made for all! — Donald J. Trump (@realDonaldTrump) April 21, 2018

South Korea's presidential office also welcomed North Korea's announcement as "meaningful progress" toward the denuclearization of the Korean Peninsula. Presidential official Yoon Young-chan said in a statement that the North's decision brightens the prospects for successful talks between Seoul, Pyongyang and Washington.

Japanese Prime Minister Shinzo Abe offered a more guarded reaction.

"What is crucial here ... is how this development is going to lead to the complete, verifiable and irreversible dismantlement of nuclear arms, weapons of mass destruction and missiles," he said. "And I will keep a close eye on that."

China, North Korea's main ally, welcomed Pyongyang's decision. The official Xinhua News Agency quoted Foreign Ministry spokesman Lu Kang as saying Beijing wishes for North Korea to continue to achieve results in the development of its economy and improving the living standards of its people. He said China will support North Korea through dialogue and consultations with "relevant parties" to resolve their concerns and improve relations.

Kim Dong-gil, the director of the Korean Peninsula Center at Peking University, says now that North Korea has nuclear weapons, he believes they will use them as a bargaining chip to officially end the 1950-53 Korean War, make arrangements to guarantee North Korea's safety and ultimately allow North Korea to open up its economy to the rest of the world.

Pyongyang residents, who have been largely kept in the dark about Kim's plans to meet Mr. Trump, gathered at subway stations, where newspapers are posted for the public, or around large screens in city plazas to see the reports. One resident, 34-year-old Son Kum Chol, said he read the news in the ruling party's newspaper. North Koreans are extremely cautious when speaking to the media, but Son told The Associated Press that the news made him feel the "future road will be brighter and prosperous."

Some analysts believe Kim feels he is entering the summit negotiations from a position of strength and is hoping to achieve tacit recognition that his country is now a nuclear power. They believe he wants to engage in talks and make some concessions around the edges that would convince Washington and other countries to ease sanctions on his struggling economy.

In his speech at the party meeting, Kim praised his nuclear policy as "a miraculous victory" achieved in just five years. A resolution passed after his speech also stressed that the country had successfully achieved its goals of obtaining a viable nuclear force and suggested it intends to keep that force.

People walk past a television news screen showing a file footage of North Korean leader Kim Jong Un, at a railway station in Seoul on April 21, 2018. Jung Yeon-je/AFP/Getty Images

Using the acronym for North Korea's official name, it said the North would "never use nuclear weapons nor transfer nuclear weapons or nuclear technology under any circumstances unless there are nuclear threats and nuclear provocation against the DPRK."

"This was a smart move by Kim," Vipin Narang, an associate political science professor and nuclear proliferation expert at the Massachusetts Institute of Technology, said in an email. "Although it largely formalizes previous pledges on the moratoria from last November and March, it still leaves a lot of wiggle room for circumventing the pledges in the future, and nothing in there is irreversible. And nothing in there mentions denuclearization, of any variety."

Narang noted that North Korea has already conducted as many nuclear tests as Pakistan and India -- six -- and may indeed not need to conduct any more underground testing.

Tossing out another nugget that could be used at the summits, Kim stressed at the party meeting his desire to shift the national focus to improving the country's economy, which has been hit hard by international sanctions and the "maximum pressure" strategy pushed by Mr. Trump.

The announcement ends what had been an ominous silence from Pyongyang regarding the stunning diplomatic moves Kim has been making since the beginning of this year, including his summit with Chinese President Xi Jinping last month.

It also gives the best idea yet of what Kim intends to bring with him in his summits with Moon and Mr. Trump.

At a news conference Wednesday with Japanese Prime Minister Shinzo Abe, Mr. Trump downplayed what could be accomplished when he meets with Kim, CBS News' Errol Barnett reports.

"If I think that it's a meeting that is not going to be fruitful, we're not going to go," Mr Trump said. "If the meeting -- when I'm there -- is not fruitful, I will respectfully leave the meeting."

Seoul says Kim has expressed genuine interest in dealing away his nuclear weapons. But North Korea for decades has been pushing a concept of "denuclearization" that bears no resemblance to the American definition, vowing to pursue nuclear development unless Washington removes its troops from the peninsula.

Some important items were also left off the North's resolution -- such as midrange missile or space rocket launches -- suggesting either that the North isn't willing to go that far or that it wants to wait and see how much it can gain by further concessions once actual talks begin.

On Saturday, as global reaction to North Korea's announcement continued to pour in, Sweden's Foreign Minister Margot Wallstrom said it's "good news" that steps are being taken "to de-escalate and to defer from further bomb and missile tests," but added that "we have to keep the pressure up with the sanctions regime and everything else we are doing."

Meanwhile, the U.S. ambassador to the United Nations welcomed North Korea's announcement, and praised the way the U.N. Security Council "really came together" in order to achieve that. Speaking at an informal working meeting of the Security Council ambassadors in southern Sweden on Saturday, Nikki Haley said pressure and sanctions coming from the U.N. enabled the isolation of North Korea "until they had a good behavior, and now we are seeing they want to come to the table."

U.N. Secretary General Antonio Guterres told reporters in Sweden that he was optimistic about North Korea's decision, saying that "the path is open for the peaceful denuclearization of the Korean Peninsula."

In an earlier statement released by his office, Guterres wished the two Koreas ahead of their April 27 summit "every success in their courageous and important task of resuming sincere dialogue leading to sustainable peace on the Korean Peninsula." He also praised the establishment of a direct telephone link between the leaders of North and South Korea.