Updated

A new U.S.-Russian crew and an Italian astronaut floated into the international space station Sunday after their Russian Soyuz (search) capsule docked at the orbiting outpost, opening a mission critical for U.S. plans to return the space shuttle to flight two years after the Columbia (search) explosion.

When the hatches between the two craft opened, the three men who blasted off Friday from the Central Asian nation of Kazakhstan — Russian Sergei Krikalev (search), American John Phillips (search) and Italian Roberto Vittori — were greeted with joyful embraces by the two men who have manned the orbiting outpost for the last six months.

Cosmonaut Salizhan Sharipov presented the new arrivals with the traditional Russian welcome offering of bread and salt; later, presumably, they would dig into the fresh produce ferried by the incoming crew and the Italian fare Vittori had brought to spice up the space diet.

"We are very happy to see the new crew arrive and we wish them an excellent mission," Sharipov said over a video linkup with Russian Mission Control in Korolyov, outside Moscow.

Fred Gregory, NASA deputy administrator, congratulated Russian space officials on the flawless docking maneuvers that brought the two spaceships into a gentle embrace in orbit and said the resumption of U.S. space shuttle flights was on schedule.

"The return to flight activities for the shuttle appears to be on time," Gregory said. "We are hopeful that we'll be able to launch within the first window," which he said was May 15-June 3.

The shuttle program has been suspended for two years, with the Russian Soyuz capsule — a relatively light 7 tons — being the only means of getting astronauts to the station since Columbia disintegrated as it returned to Earth on Feb. 1, 2003. Russian cargo ships alone have delivered fresh supplies during the interim.

American astronaut Phillips will have the key task of observing the condition of the insulating tiles as the Discovery approaches the station by conducting a photo survey of the exterior of the shuttle while it is maneuvering prior to docking. NASA has concluded that a gash in Columbia's insulted wing caused that crash.

After the newcomers opened the hatch and changed out of their bulky spacesuits into tracksuits bearing the insignia of their respective space agencies, Gregory and other officials wished the overlapping crews success.

"I want to congratulate each of you for the work you've done in the past and the work that we anticipate will be done by the Expedition 11 crew," he said.

Following tradition, the new crewmen will conduct scientific experiments, about 70 percent of them devoted to medical research, said Vladimir Solovyov, Mission Control chief.

At Russian Mission Control in Korolyov, outside Moscow, engineers monitored the docking via a video feed from a camera affixed to the spaceship and broke into applause when they saw that the automatic parking system had operated flawlessly.

Valery Lyndin, a mission control spokesman, told the ITAR-TASS news agency on Saturday that the outgoing crew members had tidied up the orbital home for the new arrivals, cleaning all inner panels and equipment with special napkins.

A dozen men in colorful Italian military uniforms were on hand in Korolyov on Sunday to mark Vittori's arrival at the station, and an Italian flag was draped over a balcony overlooking the monitoring hall.

The outgoing crew has also packed all their possessions, experiment results and photos and videocassettes they will take back with them to Earth, he said.

Cosmonaut Sharipov and U.S. astronaut Leroy Chiao were due to return in a Soyuz capsule along with Vittori on April 25.

The 46-year-old Krikalev has logged 624 days in space on missions both to the ISS and the Russian space station Mir. At the end of the current mission, his sixth, Krikalev will have spent 800 days in space — more than any other astronaut.