NASA officials said yesterday that food is running so low aboard the International Space Station that flight controllers have instructed the crew to cut back on calories. The crew may have to leave the station if a scheduled supply flight fails to arrive on Christmas Day. The Russian supply ship, Progress, should reach the hungry crew by Dec. 25.

Astronaut Leroy Chiao and Russian cosmonaut Salizhan Sharipov had enough food to last one to two weeks beyond Christmas.

International Space Station rules call for crews to begin evacuation planning if food, water or breathable air supplies fall below a 45-day supply.

This cargo ship , loaded with seven extra containers of food, "is very critical," said Bill Gerstenmaier, Nasa's space station program manager, "There's no question about that."

Progress cargo ships can carry about two and a half tons of material, about a third of what a shuttle can deliver.

If something should delay the Progress from launching to the space station then NASA will have to evacuate the crew. In this scenario, the pair would set off in the Soyuz escape capsule that is always docked at the space station.