Image copyright AFP/Getty Images Image caption Donald Trump and Kim Jong-un are due to meet in May, though North Korea has not publically confirmed this

North Korea has promised the US it is ready to discuss the future of its nuclear arsenal when the two nations' leaders meet, US officials say.

Preparations for the summit have included secret, direct talks with North Korea, unnamed Trump administration sources said.

US and North Korean intelligence officials are said to have spoken many times, and met in a third country.

The unprecedented summit is slated to happen in May.

It will be the first time a sitting US president has met the leader of North Korea.

North Korea has already told South Korea it was prepared to address denuclearisation, but this is the first time assurances have been given to Washington directly, the US officials claimed.

Details of the summit, including the timing and location, remain unclear.

Media playback is unsupported on your device Media caption Donald Trump and Kim Jong-un: From enemies to frenemies

News of proposed talks between Donald Trump and Kim Jong-un surprised many when it broke in March.

It followed a year of threats, personal insults and nuclear brinkmanship between their respective leaders.

The North has previously halted missile and nuclear tests during past talks, only to resume them when it lost patience or felt its demands were not being met.

Image copyright Reuters Image caption South Korea says the North is prepared to discuss getting rid of its nuclear arsenal if its own safety can be guaranteed

Analysis: Decoding 'denuclearisation'

By Laura Bicker, BBC Seoul Correspondent

Finally, after months of speculation, there is an acknowledgment that Washington and Pyongyang are talking to one another.

Having an open channel of communication is a huge step forward for two countries that were exchanging insults this time last year. The meeting between President Moon Jae-in and Kim Jong-un on 27 April will be also be key to getting a clearer idea of what North Korea really wants and will help prepare the US for its talks with the young leader.

However, many are worried that there may be a miscommunication right from the offset.

The unnamed US official said that North Korea was willing to discuss denuclearisation. That term could mean very different things to the US and North Korea. The US wants Kim Jong-un to give up his nuclear arsenal which North Korea has spent decades developing at a huge cost to the people of the country.

North Korea has repeatedly called for the withdrawal of US troops from the Korean peninsula and a guarantee that the US will not use its weapons to defend South Korea and Japan. Both sides may want to talk about denuclearisation. But they interpret the word rather differently, and that could make all the difference when the two leaders come face to face.

The road to talks

As yet, North Korea has not broken its public silence to confirm the summit with the US is happening.

However, a series of meetings with overseas leaders suggest that preparations are indeed under way.

In late March, Mr Kim made his first known foreign trip since taking office in 2011 - to Beijing.

The visit, confirmed by China and North Korea, involved "successful talks" with President Xi Jinping, China's Xinhua news agency reported.

Media playback is unsupported on your device Media caption Chinese TV showed footage of the two leaders with their wives

China is North Korea's main economic ally, and it was thought highly likely that Pyongyang would consult Beijing before holding summits with South Korea and the US.

South Korea has played a key role in brokering the proposed talks between the US and its northern neighbour.