The launch date has been pushed back several times since its originally designated launch in April 1998 because of cash shortages in the Russian space agency, and the delay has held up the entire 16-nation, $60-billion project.
The service module, a 24-ton cylinder that will house the first crews and includes the station's sewage system, is necessary for astronauts to live for extended periods on the outpost in space.
Tommy Holloway, NASA's station program manager, and Valery Ryumin, a deputy chief of the Russian company that built the module, said the component will blast off July 12 on top of a Proton rocket from the Baikonur launch pad.
The module was finally ready last summer but then two successive crashes of Proton rockets worried International Space Station officials, who pushed the launch further back amid fears of a launch failure. Later successful liftoffs have allayed those concerns.
"This is natural -- in dealing with technical equipment you cannot expect everything to be on time to a day," Ryumin said.
The U.S. space agency invited Russia into the station program in 1993 in hopes of saving time and money, but Russian delays are estimated to have cost NASA as much as $3 billion.
The station's first components, one made in Russia and one in America but both paid for by the U.S. government, were launched in November and December 1998. U.S. space shuttle crews have visited the fledgling station.
NASA is targeting an Oct. 30 liftoff for the first crew to be led by U.S. astronaut Bill Shepherd, though some observers call that optimistic.
The Russian side is already preparing for possible glitches: Ryumin said if the Zvezda service module fails to dock automatically with the space station components already in orbit, two Russian cosmonauts will blast off on Aug. 10 to dock it manually.
Even before reaching orbit, Zvezda has already been given bad marks from the General Accounting Office, the investigative arm of the U.S. Congress. The GAO warned in March that the station crews will face increased risk and noise because of Russia's failure to meet NASA safety standards.
It also said that the module's aluminum and magnesium skin doesn't offer strong enough protection against collisions with space junk and its equipment will fail if cabin pressure is lost, jeopardizing the entire station.
NASA said it knows about the problems and promised they would be resolved in orbit.
"Our problems will be overcome and we will accomplish our goals," Holloway said.