WASHINGTON (BLOOMBERG, AFP) - US President Donald Trump and North Korean leader Kim Jong Un will meet near the end of February for a second summit, despite evidence North Korea is advancing its nuclear weapons programme.

The White House announced the summit and timing after Trump met on Friday (Jan 18) with Kim Yong Chol, a top aide to the North Korean leader and a former spy chief.

Trump's decision to go ahead with another in-person meeting - further elevating Kim's global profile - underscores the President's confidence that his personal involvement and negotiating skills can change the behaviour of recalcitrant regimes in ways that traditional leverage and diplomacy, past US leaders and his own emissaries could not.

"President Donald J. Trump met with Kim Yong Chol for an hour and half, to discuss denuclearisation and a second summit, which will take place near the end of February," White House Press Secretary Sarah Sanders said in a statement released after the meeting.

"The President looks forward to meeting with Chairman Kim at a place to be announced at a later date."

UN chief calls for denuclearisation road map

Attention on Saturday turned to Stockholm, with North Korea's top envoy Choe Son Hui and her South Korean counterpart, Lee Do-hoon, both expected to be in town.

The State Department said the US' special representative for North Korea, Stephen Biegun, would also attend an international conference in Sweden this weekend, but stopped short of saying whether he would secure his first meeting with Choe.

Meanwhile North Korean Vice-Foreign Minister Sin Hong-chol, who is in charge of Russian affairs, arrived in Beijing on Saturday. "I have something to do in Beijing," Sin told reporters at the Beijing Capital International Airport, according to South Korean news agency Yonhap.

Kim Jong Un had visited Beijing and held a summit with Xi Jinping earlier this month, in what was seen as a consultation with the Chinese President ahead of his second summit with Trump.

Separately at the United Nations, UN Secretary-General Antonio Guterres urged the United States and North Korea to agree on a road map for serious negotiations on scrapping Pyongyang's nuclear and ballistic weapons.

"We believe it's high time to make sure that the negotiations between the United States and the Democratic People's Republic of Korea start again seriously and that a road map is clearly defined for the denuclearisation of the Korean peninsula," Guterres told a start-of-the-year news conference.

Asked about a possible easing of sanctions on the North, Guterres said he would not "advocate for any anticipation of other measures before a clear negotiation is put in place" but added that "the two things will be inevitably interlinked".

The United States has insisted that "maximum pressure" from a raft of tough sanctions imposed on North Korea by the UN Security Council must remain in place until Pyongyang has fully scrapped its nuclear and ballistic missiles programme. But North Korea insists that easing sanctions would build trust along the way to denuclearisation - a stance that has won support from China and Russia.

Guterres said the UN would not seek to play a bigger role in efforts to denuclearise the Korean peninsula, leaving the diplomacy firmly in the hands of Washington and Pyongyang.

Trump and Kim Jong Un held their unprecedented first summit in Singapore in June, concluding with a vaguely worded deal that both sides interpreted differently.

While Trump has credited Kim's decision to halt weapons tests and dismantle a few testing facilities with preventing a war in Asia, those moves haven't stopped North Korea from continuing a nuclear programme that puts the US and key allies at risk.

Satellite-imagery analysis and leaked American intelligence suggest North Korea has churned out rockets and warheads as quickly as ever in the year since Kim halted weapons tests and paved the way for his first meeting with Trump.

One arms control group estimated Kim has gained enough fissile material for about six more nuclear bombs, bringing North Korea's total to enough for between 30 and 60.

Without disclosures and inspections, it's impossible to know exactly what weapons North Korea possesses.

After Trump and the North Korean envoy's meeting on Friday, the US administration had nothing to say about the substance of the day's meetings or what would be gained from a second summit.

The lack of details only raised new questions, particularly because so little progress has been made towards the ultimate US goal - getting North Korea to give up its nuclear weapons - since the first summit between Trump and Kim in Singapore in June.

"I don't think we have any concrete agreement," said Sue Mi Terry, a former CIA analyst who's now at the Centre for International and Strategic Studies in Washington. "Obviously Kim doesn't want to meet with the bureaucrats who would make him agree to something, and I think Trump would welcome the distraction right now."

Trump's decision to go ahead with another in-person meeting - further elevating Kim's global profile - underscores the president's confidence that his personal involvement and negotiating skills can change the behaviour of recalcitrant regimes in ways that traditional leverage and diplomacy, past US leaders and his own emissaries couldn't.

In speeches, state media commentaries and meetings with his Chinese and South Korean counterparts, the once-reclusive North Korean leader has laid out a list of demands to break the deadlock in nuclear talks.

His agenda ranges from restarting economic projects frozen by sanctions to formally ending the 1950-53 Korean War to weakening the US-South Korean military alliance.

Stumbling blocks to a second summit have been North Korea's insistence that it get relief from crippling economic sanctions, and Pyongyang's demands that any disarmament deal with Trump include the removal of America's nuclear-capable planes and warships from the region.

That's the North Korean interpretation of the pledge at the previous Trump-Kim summit to work towards "denuclearisation of the Korean Peninsula."

'Nibble Around the Edges'

One possible solution would be what South Korean officials call "corresponding measures" to reward North Korean steps towards shedding its nuclear arsenal. The US could, for example seek, the destruction of the Yongbyon nuclear processing site, while allowing some trade between North and South Korea to be exempted from sanctions.

Other possible options could include a North Korean promise to stop producing new fissile material, or a peace declaration bringing a formal end to the 1950-53 Korean War.

But none of those would tackle the American objective: getting North Korea to give up its nuclear weapons for good, and allowing international inspectors to verify that it's done so.

"There are ways that they can nibble around the edges," said Jung Pak, a senior fellow at the Brookings Institution. "There are things on the periphery that they can talk about that will advance some goals and keep the ball moving on diplomacy. But we're still locked horns on the nuclear issue."

South Korea welcomed the news of a second Trump-Kim summit. The summit will be a turning point for permanent peace on the Korean Peninsula, presidential spokesman Kim Eui-keum told reporters in a text message.

'Real Progress'

Analysts have long been on the lookout for talks between the two envoys as a sign that the sides were finally getting down to detailed discussion towards specific agreements.

"That would be real progress," said Vipin Narang, a political science professor at the Massachusetts Institute of Technology. "We give up swinging for the fences and just get on base. The question is whether there's enough time between now and February to hammer out the details."

Trump has long signalled his interest in a second meeting with Kim, and there's been speculation a summit could take place in Vietnam. US officials met their North Korean counterparts in Hanoi for discussions to adjust scheduling for the talks, the South Korean newspaper Munhwa Ilbo reported.

Vietnam is a long-standing ally of Pyongyang that has good relations with Washington. Speculation about the country's prospects as a summit site grew after North Korean Foreign Minister Ri Yong Ho's visit there from Nov 29 to Dec 2.

Hanoi - about a four-hour direct flight from Pyongyang and in airspace over countries friendly to North Korea - boasts several world-class hotels. Vietnam's ruling Communist Party also has the security apparatus to squelch protests and keep curious onlookers far away from Trump and Kim.