The module carrying a US satellite to monitor global carbon dioxide emissions failed to separate from its rocket soon after it was launched early on Tuesday, NASA said.
"It appears that there were problems separating" and the satellite "did not achieve orbit," said NASA TV announcer George Diller.
"We are still evaluating the status of the location and the exact state" of the spacecraft, he said.
"We have not had a successful launch tonight," he added.
The satellite was launched from Vandenberg Air Force Base in California aboard a Taurus XL rocket at 1:55 am (0951 GMT), live images on NASA TV showed.
The mission of the Orbiting Carbon Observatory (OCO) was to map the global distribution of carbon dioxide and study how that distribution changes over time, NASA said in a statement.
It is NASA's first spacecraft dedicated to studying carbon dioxide. In January, Japan launched a satellite on a similar mission.
Carbon dioxide is the leading greenhouse gas driving climate change.
However "several minutes into the flight, launch managers declared a contingency when the fairing failed to separate properly," NASA said in a brief statement.