North Korea's foreign minister has told the United Nations that continued sanctions are deepening its mistrust in the United States, and there was no way the country would give up its nuclear weapons unilaterally under such circumstances.

Ri Yong-ho told the world body's annual General Assembly that North Korea had taken "significant goodwill measures" in the past year, such as stopping nuclear and missiles tests, dismantling the nuclear test site, and pledging not to proliferate nuclear weapons and nuclear technology.

"However, we do not see any corresponding response from the US," he said.

"Without any trust in the US there will be no confidence in our national security and under such circumstances there is no way we will unilaterally disarm ourselves first."

Mr Ri reprised familiar North Korean complaints about Washington's resistance to a "phased" approach to denuclearisation under which North Korea would be rewarded as it took gradual steps.

However his statement appeared significant in that it did not reject unilateral denuclearisation out of hand as Pyongyang has done in the past.

Mr Ri referred to a joint statement issued by Kim Jong-un and Donald Trump when Mr Kim pledged to work toward "denuclearization of the Korean peninsula" while Mr Trump promised guarantees of North Korea's security.

North Korea has been seeking a formal end to the 1950-53 Korea War, but the United States has said Pyongyang must give up its nuclear weapons first.

Washington has also resisted calls to relax tough international sanctions on North Korea.

"The US insists on the 'denuclearizsation-first' and increases the level of pressure by sanctions to achieve their purpose in a coercive manner, and even objecting to the 'declaration of the end of war,'" Mr Ri said.

"The perception that sanctions can bring us on our knees is a pipe dream of the people who are ignorant about us. But the problem is that the continued sanctions are deepening our mistrust," he added.

Mr Ri made no mention of plans for a second summit between Mr Kim and Mr Trump that the US leader highlighted at the United Nations earlier in the week.

The minister instead highlighted three meetings between Mr Kim and South Korean leader Moon Jae-in in the past five months and added: "If the party to this issue of denuclearisation were South Korea and not the US, the denuclearisation of the Korean peninsula would not have come to such a deadlock."

Even so, the tone of Mr Ri's speech was dramatically different from last year, when he told the UN General Assembly that targeting the US mainland with North Korea's rockets was inevitable after "Mr Evil President" Trump called Mr Kim a "rocket man" who was "on a suicide mission".

This year at the United Nations, Donald Trump, who last year threatened to "totally destroy" North Korea, heaped praise on Mr Kim for his courage in taking steps to disarm, but said much work still had to be done and sanctions must remain in place.

On Wednesday, Mr Trump said he did not have a time frame for this, saying "If it takes two years, three years or five months - doesn't matter."

China and Russia argue that the UN Security Council should reward Pyongyang for steps taken.

However, US Secretary of State Mike Pompeo told the UN Security Council on Thursday that: "Enforcement of Security Council sanctions must continue vigorously and without fail until we realise the fully, final, verified denuclearisation."

The Security Council has unanimously boosted sanctions on North Korea since 2006 in a bid to choke off funding for Pyongyang's nuclear and ballistic missile programs.

Mr Pompeo met Mr Ri on the sidelines of the UN General Assembly and said afterwards that he would  visit Pyongyang again next month to prepare for a second summit.