A South Korean ruling party lawmaker claimed North Korean hackers stole a large amount of classified military documents last year, including the allies' operational plan to "decapitate" the North Korean leadership.
"I can assure you that we are confident in the security of our operations plans and our ability to deal with any threat from North Korea," Pentagon spokesman Army Col. Rob Manning told reporters.
He declined to confirm whether there was a breach, calling it a matter of intelligence.
"The ROK-US alliance remains steadfast in their commitment to make sure they safeguard that information and ensure readiness on the Korean Peninsula to counter any North Korean threats," he added. ROK is the acronym of South Korea's official name, the Republic of Korea.
Tensions have run high in the wake of North Korea's ballistic missile and nuclear tests, with US President Donald Trump threatening to "totally destroy" the nation if necessary.
Trump recently doubled down on his rhetoric, saying "only one thing will work" to end North Korea's nuclear weapons program. The president is widely reported to be considering military options against Pyongyang.
Manning said the US will remain "postured" to deal with any North Korean threat. But he also noted Washington is focused on using diplomacy to resolve the impasse.
According to Rep. Lee Cheol-hee of the Democratic Party, who cited unnamed defense officials, North Korea stole 235 gigabytes of military documents, of which nearly 80 percent have yet to be identified.
Among them were contingency plans for the South's special forces, reports to the allies' top commanders, and information on key military facilities and power plants, he said.
"We'll continue to work closely with our partners in the international community in identifying, tracking and countering any cyber threats," Manning said. (Yonhap)