North Korea is ready to give the United States a "severe lesson" with its strategic nuclear force if it takes military action, and will not put its nuclear program or missiles on the negotiating table, North Korea's foreign minister said in a statement to a regional meeting on Monday.

In a transcript of a statement by Ri Yong-ho — which was distributed to media in Manila — Pyongyang called new UN sanctions "fabricated," and warned there would be "strong followup measures" and acts of justice.

The foreign minister said North Korea's intercontinental ballistic missile tests in July proved that the entire U.S. was in its firing range, and those missiles were a legitimate means of self-defence.

North Korea also vowed to bolster its nuclear arsenal and launch "thousands-fold" revenge against the United States in response to the sanctions.

U.S. Secretary of State Rex Tillerson, meanwhile, held open the door for dialogue, saying Washington was willing to talk to Pyongyang if it halted a series of recent missile test launches.

"When the conditions are right, then we can sit and have a dialogue around the future of North Korea so they feel secure and prosper economically," Tillerson told reporters on Monday.

Tillerson's comments were the latest U.S. attempt to rein in Pyongyang's nuclear and missile programs after months of tough talk from U.S. President Donald Trump.

"The best signal that North Korea can give us that they are prepared to talk would be to stop these missile launches," said Tillerson, adding that "other means of communications" were open to Pyongyang.

North Korea's warning came two days after the UN Security Council unanimously approved new sanctions to punish North Korea, including a ban on coal and other exports worth over $1 billion US.

The U.S. ambassador to the UN, Nikki Haley, called the U.S.-drafted resolution "the single largest economic sanctions package ever levelled against" North Korea.

Nikki Haley, U.S. ambassador to the United Nations, called the U.S.-drafted sanctions 'the single largest economic sanctions package ever levelled against' North Korea. (Joshua Roberts/Reuters)

'Violent infringement of its sovereignty'

In a statement carried by state media, the North Korean government said the sanctions were a "violent infringement of its sovereignty" that was caused by a "heinous U.S. plot to isolate and stifle" North Korea.

The government said the UN sanctions will never force the country to negotiate over its nuclear program or to give up its push to strengthen its nuclear capability as long as U.S. hostility and nuclear threats persist. The North said it will take an "action of justice," but didn't elaborate.

"It's a wild idea to think the DPRK will be shaken and change its position due to this kind of new sanctions formulated by hostile forces," said the statement, carried by the North's official Korean Central News Agency. DPRK stands for the North's official name, the Democratic People's Republic of Korea.

The North's statement "rhetorically expresses its anger" against the UN sanctions, but the country is not likely to launch a direct provocation against the United States, said Lim Eul Chul, a North Korea expert at South Korea's Kyungnam University. He said the North could still carry out new missile tests or a sixth atomic bomb test in the coming months under its broader weapons development timetable.

North Korean Foreign Minister Ri Yong-ho called new UN sanctions 'fabricated' and warned there would be 'strong followup measures,' saying the UN has abused its authority. (Reuters)

2 missile test launches last month

North Korea test launched two ICBMs last month as part of its efforts to possess a long-range missile capable of striking anywhere in the mainland U.S. Both missiles were fired at highly lofted angles and analysts say the weapons could reach parts of the United States including Alaska, Los Angeles and Chicago if fired at a normal, flattened trajectory.

The centrepiece of the UN sanctions is a ban on North Korean exports of coal, iron, lead and seafood products — and a ban on all countries importing those products, estimated to be worth over $1 billion US a year in hard currency. The resolution also bans countries from giving any additional permits to North Korean labourers, another source of foreign currency for the North, and prohibits all new joint ventures with North Korean companies.

According to a Security Council diplomat, coal has been North Korea's largest export, earning $1.2 billion US last year. It was then restricted by the Security Council in November to a maximum of $400 million US. This year, Pyongyang is estimated to have earned $251 million US from iron and iron ore exports, $113 million US from lead and lead ore exports, and $295 million US from fish and seafood exports, the diplomat said. The diplomat was not authorized to speak publicly and insisted on anonymity.

Analysts say that North Korea, already under numerous UN and other international sanctions, will feel some pains from the new UN sanctions but won't likely return to disarmament negotiations anytime soon because of them.

Lim said the North will likely squeeze its ordinary citizens to help finance its nuclear and missile programs.

Shin Beomchul, of the Seoul-based Korea National Diplomatic Academy, said the North won't likely return to disarmament talks unless there are sanctions that require China to stop sending its annual, mostly free shipment of 500,000 tons of crude oil to North Korea and order UN member states to deport the existing tens of thousands of North Korean workers dispatched abroad.