MOSCOW, May 21 (RIA Novosti) - NASA has given astronauts on board the International Space Station (ISS) permission to drink water that the station's new recycling system has purified from urine.

The decision was transmitted to the crew on Wednesday following a series of tests conducted by NASA experts on 20 liters of recycled water brought back to Earth by several space shuttle expeditions.

"The decision is an important milestone in the development of the station's environmental and life support systems, which will begin supporting six-person crews at the end of May," NASA said in a statement posted on its website.

Current ISS crew Commander Gennady Padalka and Flight Engineers Mike Barratt and Koichi Wakata celebrated the decision with a toast in the Destiny laboratory, NASA said.

"We are really happy for this day and for the team that put this together. This is the kind of technology that will get us to the moon and further," the U.S. space agency quoted Mike Barratt as saying.

NASA has spent decades perfecting a system to transform urine into water that can be used in space for drinking, food preparation and washing. Agency officials say the water from the system is cleaner than U.S. tap water.

Space shuttle Endeavour's STS-126 mission delivered the $250-mln Water Recovery System to the station in November 2008 and it has been in operation since March.

The system is tied into the station's Waste and Hygiene Compartment toilet and processes urine through six steps, including the addition of iodine to kill microbes. It also recovers and recycles moisture from the station's atmosphere.

"Space station crews will monitor the purity of the recycled water with on-board equipment and periodically send down samples for testing on Earth," NASA said.

NASA experts estimate the new system will provide roughly half of the crew's water intake in the future.