North Korean leader Kim Jong-Un observed the successful test of an unspecified "newly developed ultramodern tactical weapon," state media reported today, in an apparent bid to apply pressures on the United States and South Korea amid a stalemated nuclear diplomacy.

It didn't appear to be a nuclear device or a long-range missiles targeting the mainland US, a string of which last year had many fearing war before the North turned to engagement and diplomacy early this year.

Still, any mention of weapons testing could influence the direction of currently stalled diplomacy between Washington and Pyongyang that's meant to rid the North of its nuclear weapons.

The North hasn't publicly tested any weapons since November of last year, but in recent days Pyongyang reportedly expressed anger at US-led international sanctions and ongoing small-scale military drills between South Korea and the United States.

Earlier this month, North Korea's Foreign Ministry warned it could bring back its policy of bolstering its nuclear arsenal if it doesn't receive sanctions relief.

"It's a North Korea-style coercive diplomacy. North Korea is saying 'if you don't listen to us, you will face political burdens," said analyst Shin Beomchul of Seoul's Asan Institute for Policy Studies.

Mr Shin said the weapon North Korea tested could be a missile, artillery, an anti-air gun, a drone or other high-tech conventional weapons systems.

Yang Wook, a Seoul-based military expert, said a "tactical weapon" in North Korea refers to "a weapon aimed at striking South Korea including US military bases" in the South so that the North may have tested a short-range missile or a multiple rocket launch system.

Even if the test was a message for Washington and Seoul, today's report from the North was noticeably less belligerent than past announcements of weapons tests, and didn't focus on North Korean claims of US and South Korean hostility.

Mr Yang said the latest North Korean test won't completely break down nuclear diplomacy though more questions would be raised about how sincere the North is about its commitment to denuclearization.

Asked about the test, the State Department said that US and North Korean officials are talking about implementing the commitments that President Donald Trump and Kim made during their summit in Singapore in June.

The summit resulted in North Korea repeating its vague promise to achieve "complete denuclearization of the Korean Peninsula."

US Vice President Mike Pence, attending a Southeast Asian summit in Singapore, cited the "great progress" made on North Korea but said more had to be done.

A year and a half ago, "nuclear tests were taking place, missiles were flying over Japan and there were threats and propagations against our nation and nations in the region," Mr Pence said.

"Today, no more missiles are flying, no more nuclear tests, our hostages have come home, and North Korea has begun anew to return fallen American heroes from the Korean war to our soil. We made great progress but there's more work to be done."

He stressed that UN sanctions had to remain enforced.

Eugene Lee, spokeswoman of South Korea's Unification Ministry, said more analysis is necessary to find what weapon North Korea tested.

She declined to comment on Kim's inspection of the weapons test.

It's the first publicly known field inspection of a weapons test by Kim Jong-Un since he observed the testing of the Hwasong-15 intercontinental ballistic missile in November of last year, according to South Korea's Unification Ministry.

The North said the test took place at the Academy of National Defense Science and that Kim couldn't suppress his "passionate joy" at the success of the test.

He was described as "so excited to say that another great work was done by the defense scientists and munitions industrial workers to increase the defense capability of the country."

The North said this new, unspecified weapon has been under development for a long time and will help strengthen the combat power of its army.

Last year's string of increasingly powerful weapons tests, many experts believe, put the North on the brink of a viable arsenal of nuclear-tipped missiles that can target anywhere in the mainland United States.

Diplomacy has stalled since the US-North Korea summit, with Washington pushing for more action on nuclear disarmament and the North insisting that the US first approve a peace declaration formally ending the Korean War and lift sanctions.

Mr Trump and Kim are both interested in another summit, but it's unclear when it might happen.

Mr Pence has said the next meeting would allow the two leaders to put what they discussed in their last summit on paper.