Atlantis boomed off the launch pad at Cape Canaveral, Florida at 2:45 pm local time (1945 GMT) under clear blue skies and climbed toward orbit.

The shuttle's mission is transport the Columbus laboratory module -- a 1.3 billion euro ($2 billion) project financed mainly by Germany, Italy and France -- to the International Space Station. The Columbus project is part of efforts to develop the station into a jumping off point for possible trips to Mars and beyond.

A seven-person crew will man the Atlantis. They include five mission specialists, of whom two -- France's Leopold Eyharts and Germany's Hans Schlegel -- are European.

Schlegel is scheduled to make two spacewalks to connect power and fluid lines between Columbus and the station. Eyharts hopes to become the first European, long-duration station resident. He's is expected to stay in space for at least 3 months.

Watching the weather

But as with all shuttle launches, there was no guarantee things would go ahead on time.

"We're all thinking that Thursday's the day -- regardless of what the weather guy might tell you," Launch Director Doug Lyons told Reuters news agency.

The current mission was originally scheduled for last December. But that launch was postponed after NASA engineers were forced to check electrical faults with fuel gauges on the shuttle's external fuel tanks.

NASA is under considerably pressure to finish work on the space station by 2010, at which point the ageing fleet of space shuttles is due to be retired.