Kim announced his country would "no longer need any nuclear tests, mid and long and ICBM rocket tests," and therefore is suspending nuclear tests and launches of intercontinental ballistic missiles starting Saturday.
The communist country also says it is also shutting down the Poongye-ri nuclear test site where six underground tests have taken place.
The surprise announcements were delivered through North Korean state news outlet, Korean Central News Agency, and later on state TV.
Trump hailed the news of Korea suspending its nuclear tests as "very good news for North Korea and the World."
The news came earlier this week that Mike Pompeo, Trump's as-yet-unconfirmed pick for secretary of state, met with Kim in early April. No details of the talks were released, though Trump said this week the meeting went "very smoothly" and the two got along "really well."
Denuclearization of North Korea has been a key issue going into the talks between the U.S. and North Korea. The North is suspending, not freezing, its nuclear tests for now, but both Trump and South Korean President Moon Jae-in have expressed high hopes that the North is ready to give up its nuclear weapons in exchange for economic assistance.
Policy measures announced by the North’s state TV suggest that Kim aims to improve quality of living. The country's leaders is quoted as saying that North Korea's long-term economic plan is to "provide proficient and culturally [advanced] lifestyle to all people."
"North Korea's announcement signals a stepping stone for phased denuclearization," said An Chan Il, president of Seoul-based World Institute for North Korean Studies. "They are showing proof to the world that they have begun their efforts to eventually denuclearize, starting with shutting down the Punggye-ri nuclear test site. Punggye-ri test site is known to be the one and only nuclear weapon facility in North Korea at the moment. A significant slowdown in this facility was monitored in March, adding evidence that North's announcement was not a spontaneous one."
Experts have cautioned that the wording of Kim's announcement specifically mentions a "suspension" and not a "freeze."
"For North Korea to announce a nuclear freeze, they must have mentioned shutdown of the nuclear facility in Yongbyon," said Kim Yong-hyun, professor of North Korean Studies at Dongguk University in Seoul. "But this announcement said to suspend only the Punggye-ri facility and missile launches according to KCNA’s report. Still, there is a possibility open for discussion regarding Yongbyon facility which produces plutonium."
"Some say this beginning phase should be called a 'freeze,'" said Kim Kwang-jin, a former congressman at the National Assembly’s Defense Committee. "But others see a complete abolishment of already-made plutonium, uranium and missiles as a 'freeze.' That is why key terms should be clarified before the final negotiation."
South Korea's presidential office welcomed North Korea's announcement as well.
Presidential secretary Yoon Young-chan said in a written statement released Saturday, "[The] North's announcement will brighten prospects for successful talks between Seoul, Pyongyang and Washington."
The statement referred to the North’s suspending of nuclear tests and missile tests as meaningful progress toward denuclearization of the Korean peninsula.
"It is not a declaration of nuclear dismantlement because it has not yet reached the consensus of some practical compensations for the abandonment of nuclear weapons," said Cheong Seong-Chang, director of unification strategic studies program at the Seoul-based Sejong Institute.
"Since the economy has been in a state of containment after several nuclear tests and missile launches, the compromise with the international community was an inevitable choice for Kim Jong Un," Cheong added.
Japanese Prime Minister Shinzo Abe, who visited Trump in Florida this week, was more cautious in his acknowledgment of Kim's announcement of suspending nuclear tests.
"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."
ABC News' Hakyung Kate Lee contributed to this report.
Editor’s note: This story was corrected from its original version to reflect that North Korea says it is suspending nuclear testing, not its entire nuclear program.