U.S. President Barack Obama called astronauts at the International Space Station Friday to thank them for their work on the last mission of the 30-year U.S. space shuttle program.

President Obama spoke with the combined 10-person crew of the shuttle Atlantis and the space station. He jokingly told the crew that he was trying to call for pizza and did not expect to end up in space.

Mr. Obama thanked the U.S. space agency NASA and all who have worked on the shuttle program over the years, saying they have helped the United States lead the space age. He said the U.S. space program has always embodied the nation's sense of adventure, exploration and courage.

Atlantis commander Chris Ferguson called the current mission a “multinational effort” and said all the crew members at the station are “honored and privileged” to represent their home countries.

The 13-day mission is full of “lasts,” including the last spacewalk of the shuttle program, which was conducted on Tuesday. On Wednesday, the crew took on the more mundane task of unloading the more than 4,000-kilograms of cargo Atlantis hauled into orbit.

Upon its return to Earth next week, Atlantis will be retired and it and the other two space shuttles will become museum exhibits.

NASA is stopping the shuttle program to concentrate resources on deep-space exploration. The agency is working with several commercial U.S. aerospace companies to develop vehicles to replace the shuttles. Until then, Russia's Soyuz spacecraft will ferry U.S. astronauts to and from the space station, while Russian, European and Japanese cargo spacecraft will continue their resupply and waste disposal missions to the station.