At the end of April, North Korean leader Kim Jong Un made a bold statement: Pyongyang would have no reason to keep its nuclear weapons if the United States promises not to invade the country.
Mr Kim, who is Chairman of the State Affairs Commission, conveyed this when he met South Korean President Moon Jae In.
The announcement was met with varied responses, welcomed by some but greeted with scepticism by others.
The world has spent decades and umpteen rounds of talks to persuade Pyongyang to end its nuclear programme, but so far with limited success.
Pyongyang views its nuclear weapons as its strongest deterrent against destruction by a hostile outside world, and a powerful bargaining chip that can guarantee its security.
So determined was Pyongyang to achieve its nuclear aims that it doubled down even as US-led sanctions were tightened - choking its access to much-needed resources and finances - after every round of nuclear testing.
North Korea's nuclear ambition has its roots in the Korean War, which lasted from 1950 to 1953 and ended with the formal split on the peninsula into North and South with the former in the communist ambit and the latter becoming a staunch ally of the US.
Spooked by the US, which stored some of its nuclear weapons in South Korea, the founding leader of North Korea, Mr Kim Il Sung, turned to the Soviet Union for help to kick-start a nuclear programme.
The Soviets responded by supplying a research reactor and helped to develop the Yongbyon Nuclear Research Complex, which became operational in the late 1960s.
The world took notice and Pyongyang was increasingly pressured to sign up to international controls of civilian nuclear programmes in the 1970s and 1980s.
It joined the International Atomic Energy Agency (IAEA) in 1974, which allowed for international monitoring of its nuclear facilities. Eleven years later, in 1985, at the urging of the Soviet Union, North Korea signed the Non-Proliferation Treaty (NPT), from which it would later withdraw.
The early 1990s was an uneasy time for North Korea following the dissolution of its strongest ally, the Soviet Union, and as it watched a US-led multinational coalition march into Iraq after Saddam Hussein's invasion of Kuwait.
In late 1991, the US removed the last of its nuclear weapons - numbering about 100 - from South Korea as part of the Strategic Arms Reduction Treaty with the Soviet Union.
This was followed by an agreement between the two Koreas in January 1992 to denuclearise the peninsula.
But not all was well. When IAEA inspectors were allowed into the country for the first time in 1992, they encountered discrepancies between what they found and the inventory of nuclear materials North Korea reported it had, and were denied access to North Korean nuclear sites.
As a result, IAEA chief Hans Blix declared North Korea to be not in compliance with the NPT - in effect telling the world that it had gone ahead with its nuclear programme - and Pyongyang threatened to withdraw from the NPT.
It suspended the decision to withdraw after talks with the US, and, in June 1994, Mr Jimmy Carter became the first former US president to step foot in Pyongyang. He met Mr Kim Il Sung.
A month later, the North Korean leader died and was succeeded by his son, Mr Kim Jong Il.
In October, the US and North Korea signed the Agreed Framework, under which Pyongyang agreed to freeze its production of plutonium in exchange for supplies of fuel oil, economic cooperation and two light-water nuclear power plants.
Relations seemed to warm for some time, with the new millennium bringing the first inter-Korea summit since the peninsula's division.But the US, under Republican President George W. Bush, took a harder line on the North Korean nuclear programme, culminating with Mr Bush publicly denouncing the country as part of an "Axis of Evil" in a 2002 speech.
As both sides disagreed over the extent of North Korea's uranium enrichment activities, the Agreed Framework crumbled and North Korea expelled international inspectors, declaring in early 2003 that it would "no longer be bound" by the NPT.
Against this tense backdrop, the US, China, Russia, Japan, South Korea and North Korea embarked on the Six-Party Talks in August 2003.
Then US Secretary of State Colin Powell said that during the talks, Pyongyang offered to scrap its nuclear programme in exchange for major concessions from Washington, which apparently included the normalisation of ties between the two and economic assistance.
But no real breakthrough occurred and, in December 2004, Mr Bush rejected North Korea's offer to freeze its nuclear programme in return for concessions, insisting that Pyongyang dismantle the programme altogether.
The Six-Party Talks resumed in 2005 and led to a joint statement in which North Korea agreed to give up all its nuclear activities, and the US pledged that it had no intention of attacking the country. But the statement was thrown into doubt soon after, and North Korea went ahead with its first nuclear test in October 2006. Further negotiations failed, and a second nuclear test followed in May 2009.
In December 2011, power changed hands for the second time in North Korean history after Mr Kim Jong Il died.His son, Mr Kim Jong Un, became the new leader.
In the US, meanwhile, Democrat President Barack Obama, who succeeded Mr Bush in 2008, adopted a policy of "strategic patience", which involved heavier and heavier sanctions to force the Pyongyang regime to return to the negotiating table.But Mr Kim Jong Un chose to advance North Korea's nuclear programme nonetheless.
The 2016 election of Republican President Donald Trump brought yet another shift in US policy - "maximum pressure" - but also a new window for negotiations which eventually led to the unprecedented summit in Singapore.