An unmanned Russian cargo ship launched toward the International Space Station Friday while 13 astronauts inside the outpost geared up for a tough spacewalk.

The Progress 34 cargo ship lifted off at 6:56 a.m. EDT (1056 GMT), though it was mid-afternoon at its Central Asian launch site as it soared into orbit from Baikonur Cosmodrome in Kazakhstan. At the time, the linked space station and shuttle Endeavour flew 218 miles (350 km) above Sapporo, Japan.

Russia's Mission Control radioed news of the successful launch to Russian cosmonaut Gennady Padalka, who is currently commanding the station's Expedition 20 crew.

"Perfect! We'll be waiting for it," Padalka replied. "Maybe they'll bring something fresh for us."

The Progress 34 cargo ship, known in Russia as M-67, is carrying 2 1/2 tons of fresh supplies for the station's core six-man crew and is due to arrive Wednesday, a day after Endeavour's crew departs.

Packed aboard the space freighter are 110 pounds (50 kg) of oxygen, 463 pounds (210 kg) of water and 2,718 pounds (1,232 kg) of dry cargo like spare parts and science gear. The cargo ship is also delivering about 1,830 pounds (830 kg) of propellant that can be used to tweak the station's orbit when required.

Padalka and his crew are in the middle of a packed construction mission with the seven Endeavour astronauts. The shuttle arrived last week to boost the station's population to 13, its highest ever.

A station toilet broke early in the mission, but was swiftly repaired to the relief of the crowded station's joint-crew.

Endeavour astronauts have delivered a new crewmember and a Japanese experiment porch to the station while docked at the orbiting laboratory. They are performing the fourth of five spacewalks for the mission today to replace the station's oldest solar array batteries.

The shuttle crew is slated to undock on Tuesday and land July 31.