North Korea "ready for war" with USA.

North Korea has warned of “catastrophic consequences” in response to any further provocations by the US, days after a US navy battle group was sent to waters off the Korean peninsula, and was met by Donald Trump with a repeated threat of unspecified unilateral action.

The US president said on Twitter that he would “solve the problem” of North Korea if China did not provide greater help in exerting pressure on its neighbour.

The shrill rhetoric has been matched by a military build-up.

The decision to divert the USS Carl Vinson aircraft carrier and other battleships from a planned visit to Australia to the western Pacific came after tensions increased over ongoing military drills involving American and South Korean forces that Pyongyang regards as a dress rehearsal for an invasion.

“We will hold the US wholly accountable for the catastrophic consequences to be entailed by its outrageous actions,” North Korea’s state-run Korean Central News Agency quoted a foreign ministry spokesman as saying. “(North Korea) is ready to react to any mode of war desired by the US.”

The spokesman cited Washington’s refusal to rule out a pre-emptive strike against North Korean missile sites as justification for its nuclear programme.

“The prevailing grave situation proves once again that (North Korea) was entirely just when it increased in every way its military capabilities for self-defence and pre-emptive attack with a nuclear force as a pivot,” the spokesman said, according to KCNA.

“We will take the toughest counteraction against the provocateurs in order to defend ourselves by powerful force of arms.”

Meanwhile, Donald Trump took to Twitter to deliver his latest threat aimed at the Pyongyang regime.

"North Korea is looking for trouble. If China decides to help, that would be great. If not, we will solve the problem without them! U.S.A."

The tweet came in the wake of a summit meeting with Xi Jinping in Florida at the end of last week, when the Trump administration tried to persuade the Chinese president to enforce existing sanctions on North Korea more rigorously. There is no evidence that plea succeeded.

However, the threat of unilateral action is weakened by the acceptance by most of the US national security establishment that any preventative strike aimed at North Korean missile and nuclear facilities could trigger devastating reprisals against South Korea, Seoul in particular, and US bases in the region.

Last week’s US strike against a Syrian base is also being seen as a warning to North Korea, after Donald Trump said Washington was prepared to act alone if China failed to exert more pressure on its neighbour to halt its missile and nuclear weapons programmes.

North Korea again defied UN resolutions banning it from developing ballistic missile technology with another test-launch on the eve of Trump’s summit with the Chinese leader, Xi Jinping, in Florida last week.

White House officials have signalled that all options – including pre-emptive strikes – remain on the table in addressing North Korea’s steady advance towards developing long-range missiles capable of carrying a nuclear warhead as far as the US mainland.

The nuclear-powered Carl Vinson’s presence in the area coincides with speculation that North Korea could be preparing to conduct its sixth nuclear test to coincide with key dates in the country’s history, including the 105th anniversary of the birth of its founder, Kim Il-sung, on Saturday.

China’s foreign ministry, meanwhile, has played down reports that Beijing has deployed 150,000 troops to its border with North Korea.

Hua Chunying, a foreign ministry spokesperson, told reporters she was “not aware” of such a mobilisation by the People’s Liberation Army along the 880-mile border. In the past, similar reports had been proven “groundless and false,” Hua claimed.

However, with regional tensions building ahead of Saturday’s Kim Il-sung commemorations, Hua said China was “closely following” developments on the Korean peninsula.

“We believe that, given the current situation, all relevant parties should exercise restraint and avoid activities that may escalate the tension.”