An unmanned cargo ship on a vital mission docked early Sunday at the international space station, carrying badly needed food for a U.S.-Russian crew that has been forced to ration dwindling supplies.

The Progress M-51 (search) — also carrying Christmas presents from families and friends — moored at the orbiting station at 2:58 a.m. (6:58 p.m. EST Saturday), officials at Russian mission control outside of Moscow said.

The spaceship, which lifted off Friday from the remote Baikonur Cosmodrome in Kazakhstan, was carrying about 2.5 tons of food, water, fuel and research equipment for Russian cosmonaut Salizhan Sharipov (search) and U.S. astronaut Leroy Chiao (search). Included among the scientific equipment is a German-made robotic device.

Food stocks have shrunk dramatically since the two took over at the station more than two months ago, causing alarmed Russian and American space officials order them to cut back on meals.

"The docking went without any problems," said Yuri Semyonov, general engineer with the Energiya company, which manufactures the Progress. "They can greet the New Year calmly."

Chiao and Sharipov were scheduled to enter the Progress later Sunday to begin unloading the cargo.

NASA had said the men only had enough food to last two weeks beyond Christmas and will have to return to earth early if the supply mission wasn't successful. But officials at Russian Mission Control in Korolyov, just outside Moscow, sought to play down concerns, saying the crew has enough food for another month.

An international team was looking into how the station's food inventory ended up being tracked so poorly. "I don't remember in 40 years ever encountering this situation," Semyonov said.

But Alexei Krasnov, a Russian Space Agency official, said it was likely there was turkey included in the delivery for a late holiday meal.

Russian Soyuz crew capsules and Progress cargo ships have been the only link to the space station since the U.S. shuttle fleet was grounded after the shuttle Columbia burned up on re-entry February 2003, killing all seven astronauts aboard. NASA has said it plans to resume its shuttle program in May.