The Kepler space telescope launched by NASA to search for Earth-like planets in the Milky Way galaxy has reached orbit, the US space agency said.

The telescope separated from its carrier, a Delta II rocket, 62 minutes after launch from Cape Canaveral, Florida, at the altitude of more than 721 kilometres, NASA said.

Kepler will stare at the same spot in space for three and a half years, taking in about 100,000 stars around the Cygnus and Lyra constellations of the Milky Way.

At a cost of nearly $US600 million, it will be the National Aeronautics and Space Administration's first mission in search of Earth-like planets orbiting suns similar to ours, at just the right distance and temperature for life-sustaining water to exist.

Agency France-Presse