North Korea condemned its US terror listing as a "serious provocation" on Wednesday, warning that sanctions would never force it to abandon its nuclear weapons programme.

The response came shortly after China, the North's sole ally, also rejected as "wrong" new US sanctions that targeted Chinese companies doing business with the pariah state.

President Donald Trump Monday declared North Korea a state sponsor of terrorism, a spot on a US blacklist Pyongyang had shed nearly a decade ago.

On Tuesday the US unveiled its fresh sanctions which also targeted North Korean shipping, raising the pressure on the North to abandon its nuclear programme.

"Our army and people are full of rage and anger towards the heinous gangsters who dared to put the name of our sacred country in this wretched list of 'terrorism'," North Korean state news agency KCNA quoted a foreign ministry spokesperson as saying.

Slamming Washington for behaving like an "international judge on terrorism", the spokesperson added that the US move was "clearly an absurdity and a mockery to world peace and security".

Trump said that the terror designation and new sanctions would be part of a series of moves over the next two weeks to reinforce his "maximum pressure campaign" against Kim Jong-Un's regime.

But the North remained defiant on Wednesday, vowing to continue building up its nuclear force in the face of repeated US sanctions and threats.

"The nuclear weapons of the DPRK are the deterrence to safeguard our sovereignty," it said, using the initials of the North's official name.

"As long as the US continues with its anti-DPRK hostile policy, our deterrence will be further strengthened."

- 'More should be done' -

The White House has said it will not tolerate the North's testing or deployment of an intercontinental ballistic missile capable of carrying a nuclear warhead to US cities.

Experts believe Pyongyang is within months of such a threshold, having carried out six nuclear tests since 2006 and test-fired several types of missiles, including multi-stage rockets.

China has pressed for dialogue as regional tensions have soared, saying this week "more should be done" to hold talks to resolve the crisis.

But on Wednesday Beijing lashed out at the latest sanctions, which expand the list of Chinese firms accused of doing business with the North despite promises from Beijing that it will honour UN-backed punitive measures.

"We consistently oppose any country adopting unilateral sanctions based on its own domestic laws and regulations and the wrong method of exercising long-arm jurisdiction," foreign ministry spokesman Lu Kang told a regular news briefing.

Trump met China's President Xi Jinping earlier this month and is bullish about the US-China relationship, but concerns remain that Beijing is not ready to take tough measures against Kim.

While China has backed the UN measures, it has been reluctant to take the more drastic step of cutting off oil supplies through a pipeline to North Korea's lone refinery, fearing that regime collapse could lead to chaos on their common border.

And, according to US officials, some Chinese-based banks and trading firms continue to do business with the North in defiance of UN sanctions and US threats of unilateral measures.

"China has been comprehensively respecting and strictly implementing (UN) Security Council resolutions and our efforts on this regard are witnessed by all," Lu said.

The spokesman called on Washington to provide "any solid evidence" that Chinese companies have violated the UN sanctions.

He said that if any companies or individuals have violated domestic laws, "we will severely deal with that in accordance with our laws and regulations".

- Belligerent rhetoric -

A Chinese special envoy also wrapped up a four-day trip to the North on Monday, during which the two sides discussed regional concerns but made no direct statements about the nuclear standoff.

Beijing has pushed for a "dual track approach" which would see the United States freeze its military drills in South Korea while North Korea would halt its weapons programs.

Washington has rejected that approach.

US Treasury Secretary Steven Mnuchin said the sanctions would not only increase Pyongyang's isolation but also expose "its evasive tactics".

"These designations include companies that have engaged in trade with North Korea cumulatively worth hundreds of millions of dollars," Mnuchin said.

"We are also sanctioning the shipping and transportation companies, and their vessels, that facilitate North Korea's trade and its deceptive manoeuvres."

Despite Trump and Kim's belligerent rhetoric, US officials say their main goal is for Pyongyang to back down and agree to discuss disarmament.