North Korea's launch of a long-range ballistic missile is a destabilising and provocative action that violates UN Security Council resolutions, the US says.
"We condemn today's launch and North Korea's determination to prioritise its missile and nuclear weapons programs over the well-being of its people," National Security Adviser Susan Rice said in a statement on Sunday.
The US is fully committed to the security of the region, and will "defend ourselves and our allies and respond to North Korean provocations," Rice said.
North Korea said its intention was to put a satellite into orbit, but the US and its allies believe it was a cover for a test of a ballistic missile that could carry a nuclear warhead.
The launch followed a nuclear test conducted by North Korea one month ago.
"North Korea's launch using ballistic missile technology, following so closely after its January 6 nuclear test, represents yet another destabilising and provocative action and is a flagrant violation of multiple United Nations Security Council resolutions," Rice said.
Japanese Prime Minister Shinzo Abe also called the launch "absolutely unacceptable".
The rocket was launched from a facility in north-western North Korea, the South Korean news agency Yonhap reported, citing the South Korean military.