US President Barack Obama told astronauts on the International Space Station (ISS) on Wednesday that he was deeply committed to space exploration, after scrapping plans to return Americans to the moon.

Obama told the US, Russian and Japanese ISS astronauts and comrades who traveled to the station on the shuttle Endeavor that he was proud of them and the work they were doing in space.

He also said he was "committed" to human space exploration in the future, in a television link-up to the astronauts, and a question-and-answer session with high school children at the White House.

"My commitment to NASA is unwavering," Obama said during the conversation from the Roosevelt Room of the White House.

Seeking to cut the massive US budget deficit, Obama's administration has proposed scrapping the costly and over budget Constellation rocket programme designed to return Americans to the moon by 2020.

The plan, opposed by some prominent lawmakers, would see NASA concentrate on research and development that could over a longer time-frame eventually see astronauts travel outside low Earth orbit and even aim for Mars.

NASA would be encouraged to develop operations with commercial partners to fly astronauts to the ISS in low Earth orbit.

After speaking to astronauts, Obama turned over the session to selected school students, who volleyed questions at the astronauts — and even found out that it was possible to see the Golden Gate bridge from space.

The current Endeavour mission successfully attached a new room with a stunning view of Earth to the space station.

The Tranquility node and the seven-windowed cupola provide a breathtaking view of space, Earth and visiting spacecraft, while the 360-degree viewing spectrum provides a vital access point for monitoring spacewalks and docking operations.

With the new room in place, the space station is now about 90 percent complete. Endeavour is due to end its mission on 21 February.

The mission is one of just five remaining for NASA's three shuttles before the programme ends later this year after a 29-year run.