Pyongyang's declaration, long sought by Washington, will be seen as a crucial step in the fast diplomatic dance on and around the Korean peninsula.
It comes less than a week before North Korea's leader Kim Jong Un meets South Korean President Moon Jae-in for a summit in the Demilitarized Zone that divides the peninsula, ahead of a much-anticipated encounter with Trump himself.
The North had developed its weapons in what he called a "great victory", and so "no nuclear test and intermediate-range and inter-continental ballistic rocket test-fire are necessary for the DPRK now".
"The mission of the northern nuclear test ground has thus come to an end," he added at the gathering of the central committee of the Workers' Party, according to the official KCNA news agency.
The party decided that nuclear blasts and ICBM launches will cease as of Saturday - the North has not carried any out since November - and the atomic test site at Punggye-ri will be dismantled to "transparently guarantee" the end of testing.
Within minutes of the report being issued, Trump tweeted: "This is very good news for North Korea and the World - big progress! Look forward to our Summit."
Pyongyang has made rapid technological progress in its weapons programmes under Kim, which has seen it subjected to increasingly strict sanctions by the UN Security Council, the United States, the European Union, South Korea and others.
Last year it carried out its sixth nuclear blast, its most powerful to date, and tested missiles it said are capable of reaching the US mainland.
Kim and Trump traded threats of war and personal insults as tensions ramped up, and even when there was an extended pause in testing, US officials said that it could not be interpreted as a halt without an explicit statement from Pyongyang.
South Korean envoys have previously cited Kim as promising no more tests, but Saturday's news is the first such announcement directly by Pyongyang.
"Certainly this is a positive development," said Daniel Pinkston of Troy University. "It's a necessary but not sufficient step in North Korea returning to its past non-proliferation commitments."
