CAPE CANAVERAL (Reuters) - NASA will make another attempt on May 18 to launch the space shuttle Atlantis on a mission to boost the faltering orbit of the International Space Station, the U.S. space agency said Friday.

For three straight days this week NASA tried to launch Atlantis and its crew of seven but poor weather frustrated each attempt.

High winds at the Kennedy Space Center launch complex caused scrubs Monday and Tuesday and rain and winds closed emergency landing sites in Spain and North Africa on Wednesday.

When Atlantis does reach space, it will dock with the fledgling space station and astronauts will fire the shuttle's thrusters to boost the station's orbit, which is decaying at rate of about 1.5 miles (2.4 km) a week.

The crew of six Americans and one Russian will also make repairs to the Russian-built Zarya power station, one of two modules already in orbit.

Upon completion, the $60 billion science outpost will sprawl across an area the size of two football fields and have as much livable space a three typical suburban homes.

NASA said Friday that the station's orbit had fallen to 227 miles (365 km) above Earth's surface. A boost from Atlantis should restore it to 270 miles (435 km), which should keep the station safe until a Russian service module with navigation thrusters is added to the complex this summer.

Atlantis carries in its cargo bay more than 2,000 pounds (907 kg) of supplies for future crews that will aboard the station for months at a time. The first such crew is scheduled to arrive at the station before the end of the year.