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NASA expects progress, or the lack of it, next year for the agency's Commercial Orbital Transportation Services (COTS) programme to determine whether the COTS rockets can deliver cargo to the International Space Station from 2010.

Because NASA's Space Shuttle fleet is to be retired in 2010, NASA needs an alternate cargo delivery system to maintain the ISS by providing around 54,500kg (120,000lb) of food, water, equipment and spares it is obligated to deliver until its de-orbit, planned for 2016.

The agency's associate administrator for the space operations mission directorate William Gerstenmaier told Congress that it would know next year if the COTS programme, with its two competing companies, Space Exploration Technologies (SpaceX) and Rocketplane-Kistler (RpK), could provide the 9,000kg a year the station will require from NASA.

"We will know next year how well the COTS programme is progressing. They have a demonstration flight towards the end of the year and two other flights at the beginning of the year and that will give us critical information that will tell us whether COTS will be viable," says Gerstenmaier, speaking at the House of Representatives' committee on science and technology's Shuttle and ISS status hearing on 24 July.

He was responding to anti-COTS comments made at the hearing by former NASA Johnson Space Center International Space Station programme manager Tommy Holloway.

Holloway, who is also the chairman of NASA's ISS Independent Safety Task Force, said: "Depending on COTS would be a significant risk to the future viability of ISS," and that its rockets would probably not be able to deliver the necessary logistics "in a critical period" immediately after the Shuttle is retired.

To cope with this possible outcome Gerstenmaier told Congress that NASA has already planned to supply ISS with up to three years of spares with its last two Shuttle missions.