Here is a look at North Korea's nuclear capabilities and the history of its weapons program.
1985 North Korea signs the Nuclear Non-Proliferation Treaty (NPT).
1993 The International Atomic Energy Agency (IAEA) demands that inspectors be given access to two nuclear waste storage sites. In response, North Korea threatens to quit the NPT but eventually opts to continue participating in the treaty.
1994 North Korea and the United States sign an agreement. North Korea pledges to freeze and eventually dismantle its old, graphite-moderated nuclear reactors in exchange for international aid to build two new light-water nuclear reactors.
2002 January 29 - US President George W. Bush labels North Korea, Iran and Iraq an "axis of evil" in his State of the Union address. "By seeking weapons of mass destruction, these regimes pose a grave and growing danger," he says.
October - The Bush Administration reveals that North Korea has admitted operating a secret nuclear weapons program in violation of the 1994 agreement.
2003 January 10 - North Korea withdraws from the NPT.
February - The United States confirms North Korea has reactivated a five-megawatt nuclear reactor at its Yongbyon facility, capable of producing plutonium for weapons.
April - Declares it has nuclear weapons.
2005 North Korea tentatively agrees to give up its entire nuclear program, including weapons. In exchange, the United States, China, Japan, Russia and South Korea say they will provide energy assistance to North Korea, as well as promote economic cooperation.
2006 July - After North Korea test fires long range missiles, the UN Security Council passes a resolution demanding that North Korea suspend the program.
October - North Korea claims to have successfully tested its first nuclear weapon. The test prompts the UN Security Council to impose a broad array of sanctions.
2007 February 13 - North Korea agrees to close its main nuclear reactor in exchange for an aid package worth $400 million.
September 30 - At six-party talks in Beijing, North Korea signs an agreement stating it will begin disabling its nuclear weapons facilities.
December 31 - North Korea misses the deadline to disable its weapons facilities.
2008 June 27 - North Korea destroys a water cooling tower at the Yongbyon nuclear facility.
December - Six-party talks are held in Beijing. The talks break down over North Korea's refusal to allow international inspectors unfettered access to suspected nuclear sites.
2009 May 25 - North Korea announces it has conducted its second nuclear test.
June 12 - The UN Security Council condemns the nuclear test and imposes new sanctions.
2010 November 20 - A Stanford University professor publishes a report that North Korea has a new nuclear enrichment facility.
2011 October 24-25 - US officials meet with a North Korean delegation in Geneva, Switzerland, in an effort to restart the six-party nuclear arms talks that broke down in 2008.
2012 February 29 - The State Department announces that North Korea has agreed to a moratorium on long-range missile launches and nuclear activity at the nation's major nuclear facility in exchange for food aid.
2013 January 24 - North Korea's National Defense Commission says it will continue nuclear testing and long-range rocket launches in defiance of the United States. The tests and launches will feed into an "upcoming all-out action" targeting the United States, "the sworn enemy of the Korean people," the commission says.
2014 March 30-31 - North Korea warns that it is prepping another nuclear test. The following day, the hostility escalates when the country fires hundreds of shells across the sea border with South Korea. In response, South Korea fires about 300 shells into North Korean waters and sends fighter jets to the border.
2015 May 6 - In an exclusive interview with CNN, the deputy director of a North Korean think tank says the country has the missile capability to strike mainland United States and would do so if the United States "forced their hand."
May 20 - North Korea says that it has the ability to miniaturize nuclear weapons, a key step toward building nuclear missiles. A US National Security Council spokesman responds that the United States does not think the North Koreans have that capability.
December 12 - North Korea state media says the country has added the hydrogen bomb to its arsenal.
January 6-7 - North Korea says it has successfully conducted a hydrogen bomb test. A day after the alleged test, White House spokesman Josh Earnest says that the United States has not verified that the test was successful.
March 9 - North Korea announces that it has miniature nuclear warheads that can fit on ballistic missiles.
September 9 - North Korea claims to have detonated a nuclear warhead. According to South Korea's Meteorological Administration, the blast is estimated to have the explosive power of 10 kilotons.
2017 January 1 - In a televised address, Kim claims that North Korea could soon test an intercontinental ballistic missile.
January 8 - During an interview on "Meet the Press," Defense Secretary Ash Carter says that the military will shoot down any North Korean missile fired at the United States or any of its allies.
January 12 - A US defense official tells CNN that the military has deployed sea-based radar equipment to track long-range missile launches by North Korea.
July 4 - North Korea claims it has conducted its first successful test of an intercontinental ballistic missile, or ICBM, that can "reach anywhere in the world."
July 25 - North Korea threatens a nuclear strike on "the heart of the US" if it attempts to remove Kim as Supreme Leader, according to Pyongyang's state-run Korean Central News Agency (KCNA).
August 7 - North Korea accuses the United States of "trying to drive the situation of the Korean peninsula to the brink of nuclear war" after the UN Security Council unanimously adopts new sanctions in response to Pyongyang's long-range ballistic missile tests last month.
August 9 - North Korea's military is "examining the operational plan" to strike areas around the US territory of Guam with medium-to-long-range strategic ballistic missiles, state-run news agency KCNA says. The North Korea comments are published one day after President Donald Trump warns Pyongyang that if it continues to threaten the United States, it would face "fire and fury like the world has never seen."
September 3 - North Korea carries out its sixth test of a nuclear weapon, causing a 6.3 magnitude seismic event, as measured by the United States Geological Survey. Pyongyang claims the device is a hydrogen bomb that could be mounted on an intercontinental missile. A nuclear weapons monitoring group describes the weapon as up to eight times stronger than the bomb dropped in Hiroshima in 1945. In response to the test, Trump tweets that North Korea continues to be "very hostile and dangerous to the United States." He goes on the criticize South Korea, claiming that the country is engaging in "talk of appeasement" with its neighbor to the north. He also says that North Korea is "an embarrassment to China," claiming Beijing is having little success reining in the Kim regime.
November 1 - A US official tells CNN that North Korea is working on an advanced version of its intercontinental ballistic missile that could potentially reach the United States.
November 28 - A South Korean minister says that North Korea may develop the capability to launch a nuclear weapon on a long-range ballistic missile at some point in 2018.
January 2 - Trump ridicules Kim in a tweet. The president says that he has a larger and more functional nuclear button than the North Korean leader in a post on Twitter, responding to Kim's claim that he has a nuclear button on his desk.
January 10 - The White House releases a statement indicating that the Trump administration may be willing to hold talks with North Korea.
March 6 - South Korea's national security chief Chung Eui-yong says that North Korea has agreed to refrain from nuclear and missile testing while engaging in peace talks. North Korea has also expressed an openness to talk to the United States about abandoning its nuclear program, according to Chung.
March 8 - Chung, standing outside the White House, announces that Trump has accepted an invitation to meet Kim.