The countdown has begun for the space Shuttle Endeavour's launch on Tuesday, one that will bring a Canadian robotic arm to the International Space Station.

The two-armed, $200 million robot could reduce the number of space walks by a dozen per year.

The arm is called Dextre, which is short for Special Purpose Dexterous Manipulator. Canadian students came up with the nickname in a national contest.

Its uses will include exterior construction, handling experiments and changing batteries. "It is equipped with specialized grippers, built-in socket wrenches, four robotic tools, video equipment, lights, umbilical connectors to provide power and data connectivity, and a stowage platform," the Canadian Space Agency said on its website.

"Once assembled, Dextre will look a little like a human upper torso stick figure," NASA said in news briefing materials.

"It will have two arms, and be capable of performing delicate tasks and using tools. Its four cameras will give crew members inside the station views of its activities.  Dextre will be able to work from the end of Canadarm2, or from the orbiting laboratory's mobile base system."

No Canadian astronauts are on the seven-member crew of Endeavour this time. They have arrived in Florida at the John F. Kennedy Space Center.

There is one Japanese astronaut. Endeavour will be delivering the first piece of Japan's new Kibo ("Hope" in Japanese) lab on the station.

NASA forecasters say Endeavour will be able to blast off as scheduled on Tuesday, with a 90 per cent chance the weather will co-operate.

The launch is scheduled for 2:28 a.m. ET.

The mission is scheduled to last 16 days in total, from liftoff to touchdown. There are five scheduled spacewalks.