NEW YORK: North Korea is ready to halt its nuclear tests if the United States (US) suspends its annual military exercises with South Korea, the North Korean foreign minister told The Associated Press in an interview in which he also warned that his country won't be cowed by international sanctions.

Just hours after North Korea test-fired a ballistic missile from a submarine in its latest show of defiance at the US-South Korea exercises, Foreign Minister Ri Su Yong defended the country's right to increase its military readiness.

"The escalation of this military exercise level has reached its top level. And I think it's not bad ─ as the other side is going for the climax ─ why not us, too, to that level as well?" he said in his first interview Saturday with a Western news organisation, at the North Korean diplomatic mission to the United Nations (UN).

In response to the missile firing, the US State Department announced early Sunday it was restricting Ri's travel to UN functions only.

"Due to the DPRK's firing of a ballistic missile this morning, we have determined it necessary to limit the travel of the visiting foreign minister and his delegation to only those places necessary for them to conduct their UN functions," State Department spokesman John Kirby said.

Ri held firm to Pyongyang's longstanding position that the US drove his country to develop nuclear weapons as an act of self-defence. At the same time, he suggested that suspending the military exercises with Seoul could open the door to talks and reduced tensions.

"Stop the nuclear war exercises in the Korean Peninsula, then we should also cease our nuclear tests," he said. If the exercises are halted "for some period, for some years," he added, "new opportunities may arise for the two countries and for the whole entire world as well."

"If we continue on this path of confrontation, this will lead to very catastrophic results, not only for the two countries but for the whole entire world as well," he said, speaking in Korean through an interpreter.

"It is really crucial for the US government to withdraw its hostile policy against the DPRK and as an expression of this, stop the military exercises, war exercises, in the Korean Peninsula. Then we will respond likewise."

DPRK is an abbreviation for North Korea's official name, the Democratic People's Republic of Korea.

Ri, who spoke calmly and in measured words, a contrast to the often bombastic verbiage used by the North's media, claimed the North's proposal was "very logical".

It is extremely rare for top North Korean officials to give interviews to foreign media, and particularly with Western news organisations.

Ri's proposal, which he said he hoped US policymakers would heed, may well fall on deaf ears.

North Korea, which sees the US-South Korean exercises as a rehearsal for invasion, has floated similar proposals to Washington in the past but the US has insisted the North give up its nuclear weapons programme first before any negotiations. South Korea, too, is unlikely to agree to any such plan.

The result has been a stalemate that Ri said has put the peninsula at the crossroads of a thermonuclear war.

In response to Ri's remarks, a US State Department official defended the military exercises as demonstrating the US commitment to its alliance with the South and said they enhance the combat readiness, flexibility and capabilities of the alliance.

"We call again on North Korea to refrain from actions and rhetoric that further raise tensions in the region and focus instead on taking concrete steps toward fulfilling its international commitments and obligations," said Katina Adams, a spokeswoman for the State Department's Bureau of East Asia and Pacific Affairs.

Sanctions, Ri said, won't sway the North. "If they believe they can actually frustrate us with sanctions, they are totally mistaken," he said. "The more pressure you put on to something, the more emotionally you react to stand up against it. And this is important for the American policymakers to be aware of."

Ri, in New York to attend a UN meeting on sustainable development, said the possibility of conflict has increased significantly this year because the exercises have taken on what Pyongyang sees as a more aggressive and threatening tone ─ including training to conduct precision "decapitation" strikes on North Korea's leadership.

This year's exercises are the biggest ever, involving about 300,000 troops. Washington and Seoul say they beefed up the manoeuvres after North Korea conducted its fourth nuclear test, in January, which also brought a new round of tough sanctions by the UN down on Pyongyang's head. The exercises are set to continue through the end of the month.

Pyongyang, meanwhile, has responded with a series of missile launches and statements in its media that the country has developed its long-range ballistic missile and nuclear warhead technologies to the point that they now present a credible deterrent and could even be used against targets on the US mainland, though not all foreign analysts accept that claim.

Ri also used his presence at the UN conference as a forum to denounce Washington, saying in a brief statement that while North Korea is contributing to the objectives of global sustainable development by taking measures to double its production of grains to solve its food problem by 2030 and by reforesting 4.13 million acres of mountainous areas, it is doing so under "the most adverse conditions due to outside forces".

In the interview, he stated that the US has used its power to get other countries to join in pressure on North Korea.

"A country as small as the DPRK cannot actually be a threat to the US or to the world," he told the AP. "How great would it be if the world were to say to the US and the American government not to conduct any more military exercises in the Korean Peninsula... But there is not a single country that says this to the US."

"These big countries alone or together are telling us that we should calm down," he said. "For us this is like a sentence, that we should accept our death and refuse our right to sovereignty."

Ri said North Korea is not encouraged by the thawing of relations between Washington and Cuba or Iran.

"We're happy for the Cuban people and the Iranian people that they have reached successes on their path to pursuing their own goals and interests," he said. But he added that those cases "differ totally" from the US-North Korea relationship.