North Korea reportedly launched a long-range rocket that many believe is an illegal test of a ballistic missile on Saturday.
The U.S. military said shortly after that it detected a missile launch.
"U.S. Strategic Command systems detected and tracked what we assess was a North Korean missile launch into space at 6:29 p.m. CST," it said in a statement. "The missile was tracked on a southerly launch over the Yellow Sea."
Strategic Command said there was no direct threat to North America and that the military would "remain vigilant in the face of North Korean provocations and are fully committed to working closely with our Republic of Korea and Japanese allies to maintain security."
North Korea, though, is claiming it only launched a satellite.
Secretary of State John Kerry issued a statement condemning the launch as a "flagrant violation of UN Security Council Resolutions related to the D.P.R.K. [North Korea's] use of ballistic missile technology."
"This is the second time in just over a month that the D.P.R.K. has chosen to conduct a major provocation, threatening not only the security of the Korean peninsula, but that of the region and the United States as well," he said.
"We reaffirm our ironclad commitment to the defense of our allies, including the Republic of Korea and Japan."
National Security Adviser Susan Rice also condemned the launch and vowed the U.S. would "take all necessary steps" to respond.
"We condemn today's launch and North Korea's determination to prioritize its missile and nuclear weapons programs over the well-being of its people, whose struggles only intensify with North Korea’s diversion of scarce resources to such destabilizing activities," she said in a statement.
The launch is the latest provocative move from Pyongyang. It comes a month after North Korea also claimed to have successfully tested a hydrogen bomb.
The rocket launch and bomb test are both illegal under United Nations restrictions.
The move also comes days before the Senate is poised to vote on tougher sanctions on North Korea in response to the bomb test and the hack on Sony Pictures.
Jordan Fabian contributed.
This story was updated at 10:06 p.m.