NASA and its partner agencies have set a new plan to complete the International Space Station (ISS) by 2010, delaying science utilization to make way for 16 shuttle flights to piece together the orbital laboratory.

Assembly of the $100 billion space station is expected to resume in late August during NASA's STS-115 mission aboard the Atlantis orbiter. But that spaceflight depends on the results of the space agency's STS-121 return to flight mission expected to launch in May, NASA chief Michael Griffin told reporters Thursday.

"We are largely deferring utilization and we are paring logistics to the bone," Griffin said during a press conference at NASA's Kennedy Space Center in Cape Canaveral, Florida. "We don't like that. But confronted with a choice between having a high confidence to complete the assembly of the station...or utilizing it heavily as we built it and possibly not finishing, we chose the former course."

NASA has until the end of the fiscal year in 2010 - when its three remaining shuttles are due for retirement - to complete its role in the ISS assembly plan. Major construction has been sidelined since the 2003 Columbia accident.

A 17^th shuttle flight could service the Hubble Space Telescope in orbit in early 2008, Griffin said.

Image Gallery: Building the International Space Station

Earlier lab launches

Among the larger revisions for ISS assembly are earlier flights for the large station modules built for Japan and Europe. [NASA's complete ISS assembly manifest is available here].

NASA now plans to launch the European Space Agency's (ESA) billion-dollar Columbus laboratory on the seventh shuttle flight, ESA officials said.

"We appreciate the priority that all the partners, and especially NASA, have put on the Columbus module," ESA director-general Jean-Jacques Dordain said.

The first of three components for the Japanese Experiment Module (JEM) - or Kibo - are slated for 2007, one flight earlier, during the eighth scheduled orbiter mission, said Keiji Tachikawa, head of the Japan Aerospace Exploration Agency (JAXA). The remaining two components are set for the ninth and twelfth shuttle missions, he added.

The station's crew size - limited to two astronauts since the Columbia accident - is expected to return to a standard three-person complement with the arrival of ESA astronaut Thomas Reiter during the STS-121 flight this summer, Griffin said. By 2009, the station should be ready to support its intended crew of six astronauts, he added.

The new ISS assembly plan also anticipates the arrival of unmanned cargo shipments aboard Russia's Progress vehicles, ESA's Automated Transfer Vehicle - the first of which is slated for 2007 - and Japan's unmanned HTV supply ship.

Resuming construction

NASA's three space shuttles - Atlantis, Discovery and Endeavour - are the only vehicles capable of delivering major components to the ISS, including the required trusses, solar arrays and modules that make up the orbital laboratory.

Some components have been dropped from the launch manifest, among them, a Russian-built solar power platform and centrifuge module built for NASA by JAXA, though much of the station's intended hardware will fly.

"It's the same space station [as envisioned], the hardware all goes up," Griffin said. "Our early plans, which were better plans frankly, allowed us to utilize it while we were building it."

During the two- and one-half years NASA spent recovering from the 2003 Columbia accident, Russia's Federal Space Agency supported the ISS with a lifeline of unmanned Progress cargo ships and steady launches of crew-carrying Soyuz spacecraft.

The next ISS crew, Expedition 13 commander Pavel Vinogradov and flight engineer Jeffrey Williams, is set to launch toward the station on March 29 EST with Brazil's first astronaut Marcos Pontes. The current crew, Expedition 12's Bill McArthur and flight engineer Valery Tokarev, will jettison a used Progress 19 cargo ship early Friday, NASA officials said.

"I have proposed to make a stock of...Soyuz and Progress vehicles," Russia's space agency chief Anatolii Perminov said.

ISS 2015 and beyond

Perminov said Russia's Federal Space Agency has agreed to draw on the station's U.S.-built power system for some components through 2015 - in lieu of its solar power platform - and has proposed plans to continue ISS operations into 2016 and beyond.

"If NASA decides to leave the [ISS] program after 2015, and if all the modules and systems are in place, technically it will be feasible to continue the space station," Perminov said, adding that all focus is currently on the upcoming STS-121 mission.

Griffin said that it was too early to speculate what NASA and the ISS program will do in 2016, adding that if the U.S. space agency holds to its present course, and no major problems arise, there should be ample time to complete the station before the shuttle fleet's 2010 retirement.

"We have substantial schedule slack, in fact almost a full year, to complete the station," Griffin said.

• NASA Aims at May 10 for Next Shuttle Flight
• Air Apparent: New Oxygen Systems for the ISS
• Return to Flight: NASA's Road to STS-121
• The International Space Station So Far: Five Years of Service, But Incomplete