North Korean leader Kim Jong-un has visited a test site to supervise a “newly developed ultramodern weapon”, according to state media, marking the first announcement of continued weapons development since he began a rapprochement with the United States and South Korea earlier this year.

The Korean Central News Agency did not specify the exact type of weapon or when the test occurred, but the public declaration comes as talks with the US over the North’s nuclear program stall. North Korea has said it would suspend nuclear and missile tests as part of its push to improve relations with Washington, and Kim has said he is focused on improving the North’s crippled economy.

“After seeing the power of the tactical weapon, Supreme Leader Kim Jong-un was so excited to say that another great work was done by the defence scientists and munitions industrial workers to increase the defence capability of the country,” the report said.

State media said the project was begun under Kim’s father, former leader Kim Jong-il, and that the younger Kim “missed Kim Jong-il very much while seeing the great success of its test”.

A single photo accompanying the story showed Kim surrounded by military leaders taking notes, and no weapons were pictured. The last weapons test to be publicly announced was the Hwasong-15 intercontinental ballistic missile in November 2017, before a dramatic thaw in tensions on the Korean peninsula.

A spokesperson for the US state department said the US was confident that Kim would keep to the agreement made during during his summit with Donald Trump in Singapore in June.

“We remain confident that the promises made by President Trump and Chairman Kim will be fulfilled,” the spokesman said in a statement.

Despite the lack of progress in nuclear talks, US and North Korean officials are still working toward a second meeting between Kim and Donald Trump, and many observers believe it is the best opportunity for a breakthrough. Vice President Mike Pence said North Korea would not need to submit a list of its nuclear and missile inventory before a second summit, but that it would be a priority at the meeting.

“I think it will be absolutely imperative in this next summit that we come away with a plan for identifying all of the weapons in question, identifying all the development sites, allowing for inspections of the sites and the plan for dismantling nuclear weapons,” Pence said in an interview with NBC, adding “now we need to see results”.

The announcement of the North Korean weapons test comes just days after a report by a Washington think tank that highlighted the North’s continued development of undeclared medium-range missile bases, which could threaten US military forces in Asia.

It also comes less than a day after South Korea used explosives to demolish part of a guard post inside the demilitarised zone that separates the two Koreas, part of a wider agreement to withdraw forces from the border area.

Despite Trump walking away from his meeting with Kim in June declaring North Korea was no longer a threat, the two sides did not agree on any detailed plan to halt nuclear and weapons programs, instead settling on a vague declaration to work toward the “complete denuclearisation of the Korean peninsula”.