Space shuttle Discovery launches from pad 39B at Kennedy Space Center, Florida (NASA photo)

The U.S. space agency has delayed the next space shuttle mission until March 2006, ruling out the launch originally planned for September.

NASA officials are still trying to determine why a large piece of hard foam broke off from the shuttle Discovery's fuel tank during launch last month.

A similar piece of foam damaged the shuttle Columbia on liftoff and led to its break-up on re-entry in 2003.

The delay comes one day after a group of seven experts said NASA officials have compromised safety to ensure the space shuttle's return to flight.

The experts were dissenting from the report of a larger task force evaluating safety procedures in the shuttle program.

The full 25-member task force said NASA has made significant strides to correct the conditions that led to the Columbia disaster.