Defense Secretary Hagel's comments about the North's chemical arsenal come amid new concerns over the sophistication of North Korea's nuclear weapons program.
When North Korea shut down the industrial park it jointly maintained with South Korea in April, it ratcheted tensions to a new high.
Analysts say that North Korea may be holding out for a high-profile visitor from the US before allowing Kenneth Bae’s release.
North Korea missiles: Cuba says the 240 tons of weapons were being sent to North Korea for repairs. Many international observers are dubious.
On the 63rd anniversary of the Korean War that divided the peninsula, hackers hit systems in both North and South Korea.
North Korea's refusal to take South Korea's phone calls has dashed hopes for proposed peace talks.
Relations between the North and the South have been more strained than usual lately, but an agreement to discuss reopening a joint factory venture could shift the mood in the region.
Only one prisoner born in North Korea's gulag is known to have escaped to tell his story. A Q&A with Blaine Harden, the journalist who wrote about Shin Dong-hyuk.
A new UN panel is vowing to hold North Korea's Kim regime to 'full accountability' for decades of mass crime and murder. Will Pyongyang face ICC indictment?
A group of Chinese fishermen are said to be held hostage in North Korea, straining ties already frayed by North Korea's missile launches.
Mr. Bae was detained and sentenced to 15 years in prison. North Korea today spelled out its charges, which include plotting to overthrow the government.
US basketball star Dennis Rodman recently hung out with North Korea's leader Kim Jong-un - now he's tweeted a request that the American sentenced to 15 years' hard labor be released.
Many Korea watchers speculated that once joint military drills ended, so would increased tensions with North Korea. But at least one analyst says this might be the moment the North lashes out again.