SEOUL (Reuters) - North Korean leader Kim Jong Un said on Sunday that the isolated, nuclear-capable country was close to test-launching an intercontinental ballistic missile (ICBM).

North Korean leader Kim Jong Un gives a New Year address for 2017 in this undated picture provided by KCNA in Pyongyang on January 1, 2017. KCNA/via Reuters

North Korea tested ballistic missiles at an unprecedented rate during 2016, although some experts have said it is years away from developing an ICBM fitted with a nuclear warhead capable of reaching the United States.

“Research and development of cutting edge arms equipment is actively progressing and ICBM rocket test launch preparation is in its last stage,” Kim said during a televised New Year’s Day speech.

The country has been under U.N. sanctions since 2006 over its nuclear and ballistic missile tests. The sanctions were tightened last month after Pyongyang conducted its fifth and largest nuclear test on Sept. 9.

A successful ICBM test launch would mark a significant step forward for secretive Pyongyang’s weapons capability. ICBMs have a minimum range of about 5,500 km (3,418 miles), but some are designed to travel 10,000 km (6,214 miles) or further. California is roughly 9,000 km (5,592 miles) from North Korea.

However, North Korea has struggled to reliably deploy its intermediate-range Musudan ballistic missile, succeeding just once in eight attempted launches last year.

U.S. State Department spokeswoman Anna Richey-Allen on Sunday called on North Korea “to refrain from provocative actions and inflammatory rhetoric that threaten international peace and stability, and to make the strategic choice to fulfil its international obligations and commitments and return to serious talks.”

She urged “All states to use every available channel and means of influence to make clear to the DPRK and its enablers that launches using ballistic missile technology are unacceptable, and take steps to show there are consequences to the DPRK’s unlawful conduct.”

The Musudan is designed to fly about 3,000 km (1,860 miles), posing a threat to South Korea and Japan, and possibly the U.S. territory of Guam.

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South Korea’s Defence Ministry declined to comment on whether North Korea would test launch an ICBM soon.

TRUMP REQUESTED NORTH KOREA BRIEFING

According to a senior U.S. intelligence official, President-elect Donald Trump’s first, and at that time only, request for a special classified intelligence briefing was for one on North Korea and its nuclear weapons programme.

North Korea and its nuclear programme has also been of interest to retired Lieutenant General Michael Flynn, Trump’s choice for national security advisor and a former director of the Defense Intelligence Agency.

An Chan-il, a former North Korean military officer who defected to the South and runs a think tank in Seoul, said Kim will gauge Trump’s comments about his country for potential interest in dialogue and determine whether to try and conduct an ICBM test launch.

“If Trump comes in and the North does not get a good signal in terms of how the relationship between the two countries is going to go, that’ll give them another reason to do it,” An said.

Kim also said that the North would continue to develop its pre-emptive nuclear strike capability if the United States and South Korea continue to conduct annual joint military exercises.

There are 28,500 U.S. troops based in South Korea, and North Korean state media often describes annual joint exercises as preparation for an attack.

In February, North Korea launched a satellite into space, which was widely seen as a test of long-range ballistic missile technology.

A senior U.S. military official said last month that North Korea appears able to mount a miniaturised nuclear warhead on a missile but is still struggling with missile re-entry technology necessary for longer range strikes.

Although it fired a variety of missile types last year, North Korea is not known to have test-launched a ballistic missile since October.