"We have lines of communications to Pyongyang," Secretary of State Rex Tillerson said. The State Department later said North Korean officials are not "ready for talks regarding denuclearization."
It is the latest in a tit-for-tat between President Trump and the North Korean leader. In a tweet on Friday, the president said Kim Jong Un "will be tested as never before!"
Senate Foreign Relations Committee Chairman Bob Corker says his committee is considering narrowing the president's ability to launch wars without congressional approval.
Petrov was on overnight duty in 1983 when computers indicated the U.S. had launched a nuclear strike against his country. He had only a few nerve-jangling minutes to act.
In addition, most falsely believe the president needs congressional authorization to launch a nuclear strike. North Korea's renegade program will be a major focus at this week's U.N. General Assembly.
Sanctions and the threat of military action have proven ineffective at stopping North Korea's nuclear program. Some say that a deal with North Korea, with China's involvement, may be the way to go.
At a time of growing North Korean weapons capabilities, President Trump and Moon Jae-in will meet Thursday. "We will focus on building a foundation of friendship and trust," says Moon's spokesman.
President Trump is calling on North Korea to relinquish its nuclear arsenal. History suggests that's unlikely. Only one country has built its own nukes, and then given them up.
The president-elect's comments on Israel, China and nuclear policy also highlight how reactionary comments on social media can immediately spur international concern and attention.
Longstanding nonproliferation deals between the two countries are fraying. Bickering over nuclear issues has increased markedly in recent months, with each side accusing the other of cheating.
The U.S. Department of the Treasury says a Chinese conglomerate on the North Korean border has helped blacklisted North Korean companies procure raw materials that could be used for nuclear weapons.
Obama has sought to reduce the world's nuclear stockpile throughout his tenure. Yet he's also put the U.S. on course to spend some $1 trillion on upgrading its aging nuclear arsenal.
The Government Accountability Office report also finds that the nuclear system is coordinated on a 1970s-era computer. The parts are so obsolete that it's difficult to find replacements.
North Korea's powerful are gathering for their first ruling party congress in decades. Kim Jong Un is working to consolidate his power at home — and regionally — with an expanded nuclear arsenal.
North Korea's leader was speaking at the country's highest-level political gathering since 1980. This comes after it has conducted a series of provocative weapons tests.
President Obama said Donald Trump's statements on nuclear issues show he "doesn't know much about foreign policy, or nuclear policy, or the Korean Peninsula, or the world generally."
The tests may violate a U.N. Security Council resolution barring Iran from test-firing missiles capable of carrying nuclear weapons. Iran says the missiles aren't designed for nukes.
The archipelago, which was the site of dozens of U.S. nuclear tests in the 1940s and '50s, is suing India, Pakistan and the United Kingdom in the International Court of Justice.
Pyongyang says its launch is for an "observation satellite," but many nations view the launch as a concealed long-range missile test. So far, there has been no damage to boats or planes in the area.
The announcement — which has not yet been confirmed by international experts — follows a magnitude 5.1 earthquake that shook the rogue nation's nuclear test site.
The southern city was devastated three days after Hiroshima, in the closing act of World War II. At the ceremony, Prime Minister Shinzo Abe renewed his country's pledge to shun nuclear weapons.
