The arrival of the five-man, two-woman crew was delayed for a day due to poor weather from Tropical Storm Alberto.

This launch is the second since space shuttle Columbia disintegrated as it returned to Earth three years ago, killing all seven astronauts.

The dress rehearsals include a practice launch countdown set for Thursday.

"It's great to be here, finally, a day late," said Steve Lindsey, the mission's commander. "My crew and I are optimistic that early July looks good."

The crew members rearranged their schedule and planned to stay an extra day, until Friday, because of the weather delay.

The US space agency (Nasa) shuttle's primary mission is to prove safety upgrades to the orbiter, made since the 2003 Columbia accident, are working.

Strapped in

For the final two hours of the launch rehearsal on Thursday, the crew will don their bright orange, pressurised flight suits and strap themselves into their seats aboard Discovery.

Safety briefings are planned for Friday, including emergency launch pad escape procedures.

A practice countdown will be held on Thursday

Nasa managers will then begin a final pre-flight review that will look at all changes made to the shuttle and to flight procedures since Discovery's last mission a year ago.

The shuttle fleet has been grounded since then for work on the shuttle's external fuel tank. A suitcase-sized chunk of foam shed from the tank narrowly missed the orbiter during its launch in July 2005.

This was the same problem that doomed Columbia; in 2003, a foam chunk only slightly bigger than this came away from the tank on lift-off and punched a hole in its wing.

It allowed super-heated gases to enter the wing when Columbia attempted to return to Earth on 1 February 2003 and tear the shuttle apart.

Construction plans

On this mission, Discovery will fly to the International Space Station (ISS) to deliver supplies, equipment and a new crew member, the European Space Agency astronaut Thomas Reiter.

If successful, Nasa plans another 16 missions to the station to finish construction of the half-built outpost and - potentially - one last servicing call to the Hubble Space Telescope before the shuttle fleet is retired in 2010.

In addition to Lindsey and Reiter, the crew includes pilot Mark Kelly, flight engineer Lisa Nowak, British-born spacewalker Piers Sellers, fellow spacewalker Michael Fossum, and astronaut Stephanie Wilson.

The pre-flight review is expected to last until Saturday. When it concludes, Nasa is expected to set a firm launch date for Discovery, which is currently targeted to lift off between 1 and 19 July.