Kim vows to make North Korea 'strongest nuclear power'

The North has rattled the international community with a flurry of missile launches and its largest ever nuclear test in recent months in its bid to develop a warhead capable of striking the United States.

Kim told workers behind the recent test of a new missile Pyongyang said was capable of that feat, that his country "will victoriously advance and leap as the strongest nuclear power and military power in the world," in a ceremony yesterday, according to state news agency KCNA.

His comments come as global powers scramble for a response to the crisis, with the US backing stringent economic and diplomatic sanctions on Kim's regime to halt its nuclear drive.

But the North has continued to lob missiles, posing a major challenge to US President Donald Trump.

Fears of a catastrophic conflict with the nuclear-armed regime have spiked as the leaders have taunted each other, with the US President pejoratively dubbing his rival "Little Rocket Man."

Tension flared anew in the flashpoint peninsula after the November 29 launch of the Hwasong-15 ICBM, which the North claimed could deliver a "super-large heavy warhead" anywhere on the US mainland.

Many analysts suggest that the rocket is capable of reaching the US mainland but voice scepticism that Pyongyang has mastered the advanced technology needed to allow the rocket to survive re-entry to the Earth's atmosphere.

Last month's launch was the first test of any kind since September 15, and quashed hopes that the North may have held back in order to open the door to a negotiated solution to the nuclear standoff.

US Secretary of State Rex Tillerson said he was confident that Washington is doing all it can to force North Korea to discuss nuclear disarmament.

"As I've told people many times, I will continue our diplomatic efforts until the first bomb drops," he said in a speech to the Atlantic Council policy forum.

But he also warned that the US military stands ready to act if necessary.

Washington has ramped up the pressure on the North and last week the United States and South Korea launched their biggest-ever joint air exercise.

Pyongyang slammed those manoeuvres as a provocation, accusing the drills of "revealing its intention to mount a surprise nuclear pre-emptive strike."