The rush is on to fix the flush in space.

That's because three astronauts are orbiting Earth in the international space station with a balky toilet.

So folks on the ground in Florida are putting together a repair kit to send up Saturday, when seven astronauts blast off to deliver a large module, part of the Japanese space laboratory, Kibo.

The Russian-built toilet has been acting up for the past week. The three male residents have temporarily bypassed the problem, which involves urine collection, not solid waste.

The pump that astronauts plan to replace isn't something that can be picked up at the local home-repair store.

Tucked away in a diplomatic pouch from Russia and shepherded by a NASA worker, a 29-pound toilet pump was winging its way Wednesday toward Kennedy Space Center, where technicians will put it aboard the space shuttle Discovery as a last-minute addition.

If all goes well, astronauts will install a new gas-liquid separator pump, part of the system that processes the astronauts' urine.

To make room for the pump inside Discovery's crammed cabin, NASA was going to pull out some wrenches, a spare part for the space station's oxygen generator and a microbe-killing device for use in the European space lab.

"Clearly, having a working toilet is a priority for us, so some of these things that we didn't need for the next six months or so could wait," said payload manager Scott Higginbotham.

NASA is also squeezing in a Disney action figure, Buzz Lightyear. The toy popularized by the 1995 movie "Toy Story" will spend several months at the space station as part of an educational program for math and science teachers and their students.

Meanwhile, the main cargo aboard Discovery is Japan's Kibo lab, a 37-footer that's as big as a school bus. Kibo means "hope" in Japanese.

Weather forecasters said there is an 80 percent chance of good weather for the planned launch Saturday.

The seven astronauts who will be going on the 14-day mission flew from their Houston base Wednesday to Kennedy Space Center. The shuttle is scheduled to return June 14.