Message of peace:A girl writes a note next to a map of the Korean peninsula during the welcoming event for the summit between South and North Korea, in Seoul on Saturday.AP  

North Korean leader Kim Jong-un said he would halt nuclear tests and intercontinental missile launches, in a Saturday announcement welcomed by U.S. President Donald Trump ahead of a much-anticipated summit between the two men.

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 the North Korean leader meets South Korean President Moon Jae-in for a summit in the Demilitarised Zone that divides the peninsula.

But Mr. Kim gave no indication Pyongyang might be willing to give up its nuclear weapons, or the missiles with which it can reach the mainland U.S..

The North had successfully developed its arsenal, including miniaturising warheads to fit them on to missiles, Mr. Kim said, and so “no nuclear test and intermediate range and intercontinental ballistic rocket test fire are necessary for the DPRK now”.

As such, the North’s nuclear testing site was no longer needed, he told the central committee of the ruling Workers’ Party, according to the official KCNA news agency.

Test site to be shut

The party decided that nuclear blasts and Intercontinental ballistic missile (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, Mr. Trump tweeted: “This is very good news for North Korea and the World — big progress! Look forward to our Summit.”

Seoul too welcomed the announcement, calling it “meaningful progress” towards the denuclearisation of the Korean peninsula.

But Mr. Kim offered no sign he might be willing to give up what he called the North’s “treasured sword”, saying its possession of nuclear weapons was “the firm guarantee by which our descendants can enjoy the most dignified and happiest life in the world”.

Pyongyang has made rapid technological progress in its weapons programmes under Mr. Kim, which has seen it subjected to increasingly strict sanctions by the UN Security Council, the U.S., the EU, South Korea and others.

Last year it carried out its sixth nuclear blast, by far its most powerful to date, while Mr. Kim and Mr. Trump traded threats of war and personal insults as tensions ramped up.

Even when there was an extended pause in testing, U.S. officials said that it could not be interpreted as a halt without an explicit statement from Pyongyang.

South Korean envoys have previously cited Mr. Kim as promising no more tests, but Saturday’s news is the first such announcement directly by Pyongyang.

‘Promising but limited’

Analysts cautioned that the declaration was promising but limited.

“Certainly this is a positive development,” said Daniel Pinkston of Troy University. “It’s a necessary but not a sufficient step in North Korea returning to its past non-proliferation commitments.”

And Christopher Green of the International Crisis Group added on Twitter: “I don’t see how North Korean statement constitutes a step toward denuclearisation. It is a moratorium on testing, but recommits North Korea to nuclear weapons status.”

Japan — which has seen missiles fly over its territory — gave a mixed response, with Prime Minister Shinzo Abe offering a cautious welcome but his Defence Minister saying North Korea did not mention the short or medium-range missiles that put Tokyo within reach.

Beijing said it believed the move would “help to promote the process of denuclearisation and attempts to find a political settlement” on the peninsula.

The EU welcomed Mr. Kim’s announcement as “a positive, long sought-after step” on the path to complete denuclearisation.

The formal declaration of an end to testing comes after Mr. Kim reiterated the North’s nuclear status in his New Year speech and said he had a nuclear button on his desk — prompting Mr. Trump to tweet that he had a bigger one of his own.

Events have moved rapidly since then, catalysed by the Winter Olympics in the South, and Seoul is now pushing for a peace treaty to formally end the Korean War.

But there is a long way to go and Mr. Moon himself acknowledged this week that the “devil is in the details”.

The U.S. is seeking the complete, verifiable and irreversible denuclearisation of the North, while according to Mr. Moon, Pyongyang wants security guarantees, potentially leaving much space for disagreement.

But Mr. Kim told the Workers’ Party meeting: “A fresh climate of detente and peace is being created on the Korean peninsula and the region and dramatic changes are being made in the international political landscape.”