* North says nuclear development successful, no more tests needed
* Will pursue 'active dialogue' with other countries-KCNA
* All efforts to be concentrated on developing economy (Adds South Korea response, expert comments, background)
By Cynthia Kim and Soyoung Kim
SEOUL, April 21 (Reuters) - North Korea will suspend nuclear and missile tests effective immediately and abolish a nuclear test site in a bid to pursue economic growth and peace on the Korean peninsula, the North's state media said on Saturday, ahead of planned summits with South Korea and the United States.
North Korea leader Kim Jong Un said his country no longer needed to conduct nuclear tests or intercontinental ballistic missile tests because it has completed its goal of developing nuclear weapons, state media Korean Central News Agency (KCNA) said.
North Korea said that to create an "international environment favorable" for its economy, it would "facilitate close contact and active dialogue" with neighboring countries and the international community.
It marked the first time North Korea directly addressed its nuclear weapons programmes, ahead of leader Kim's planned summit with South Korean President Moon Jae-in next week and a meeting with U.S. President Donald Trump in late May or early June.
“The northern nuclear test ground of the DPRK (Democratic People's Republic of Korea) will be dismantled to transparently guarantee the discontinuance of the nuclear test," the KCNA said after Kim convened this year's first plenary session of the Central Committee of the ruling Worker's Party on Friday.
“We will concentrate all efforts on building a powerful socialist economy and markedly improving the standard of people's living through the mobilization of all human and material resources of the country,” the KCNA said.
Trump welcomed the statement and said he looked forward to a 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," Trump said on Twitter.
South Korea said the North's decision signified "meaningful" progress toward denuclearization of the Korean peninsula and would create favorable conditions for successful meetings with it and the United States.
North Korea has defended its nuclear and missile programmes as necessary deterrents against perceived U.S. hostility. It has conducted numerous missile tests, and last year it detonated its most powerful nuclear bomb.
The tests and escalating rhetoric between Trump and Kim raised fears of war until, in a New Year's speech, the North Korean leader called for reduced military tensions and improved ties with South Korea and sent a delegation to the Winter Olympics in the South in February.