North Korea has downplayed US Secretary of State Rex Tillerson's warning of a possible military strike against the country, stressing its full readiness to respond to any war.

The state-run television KRT on Tuesday cited the Foreign Ministry’s spokesman as saying that North Korea has the will and capability to fully respond to any war which the US wants.

"The nuclear force of (North Korea) is the treasured sword of justice and the most reliable war deterrence to defend the socialist motherland and the life of its people," the official Korean Central News Agency quoted the spokesman as saying.

KCNA quoted the unidentified spokesman as saying the US should accept that North Korea is a nuclear-capable nation that "has the will and capability to fully respond to any war the US would like to ignite."

"If the businessmen-turned US authorities thought that they would frighten (North Korea), they would soon know that their method would not work," the official was quoted as saying.

Last week, Tillerson issued the Trump administration's starkest warning yet to North Korea, saying a military response would be "on the table" if it took action to threaten South Korean and US forces.

Tillerson wrapped up his first Asian trip as the US Secretary of State in Japan, South Korea and China on Sunday with a main focus on finding a "new approach" on North Korea after what he described as two decades of failed efforts to denuclearize the nation.

China's Foreign Minister Wang Yi (R) and US Secretary of State Rex Tillerson arrive for a joint press conference at the Diaoyutai State Guesthouse in Beijing on March 18, 2017. (Photo by AFP)

State media on Sunday reported that North Korea had conducted a test of a new high-thrust engine at its rocket launch station and leader Kim Jong-un said the successful test marked "a new birth" of the country’s rocket industry.

North Korea has so far conducted five nuclear tests and numerous missile launches.

Meanwhile, the UN's atomic watchdog chief has warned that North Korea's uranium enrichment facility has doubled in size over the last few years.

Yukiya Amano, head of the International Atomic Energy Agency (IAEA) told the Wall Street Journal that Pyongyang’s nuclear capacities are being ramped up.

The United Nations and the European Union have already imposed an array of crippling sanctions on the North over its missile and nuclear programs. Pyongyang says the programs are meant to guarantee security against potential US military aggression.

Despite the sanctions and other forms of international pressure, Pyongyang declared itself a nuclear power in 2005, and has pledged to strengthen its military capability.

The North Korean leader accuses the US of plotting with regional allies to topple his government.

(Source: Agencies)