The Soyuz rocket, carrying Russian flight commander Yury Malenchenko and US flight engineer Edward Lu, lifted off at 0354 GMT and is due to dock with the International Space Station early Monday.

All US space missions have been grounded while investigations continue since the Columbia shuttle disintegrated and burnt up on entry, killing all seven crew members, on February 1.

The Soyuz rocket tore up into the sky in a burst of orange giving off clouds of smoke.

Clapping broke out but Lu's brother Rick and fiancee Christine waited tensely as they watched the US cosmonaut on a TV screen as a countdown began toward orbit.

They looked anxiously on as the screen went fuzzy at one point and the image went off.

But nearly nine minutes into the flight, there were smiles of relief and loud applause as it was announced that the craft had successfully reached orbit. "Oh, boy!" exclaimed Rick.

"It's ecstatic," said Christine. "I'm so relieved after that last stage. I was holding my breath. It's my first launch. The relief is overwhelming."

"We're so happy for him. He was so excited about the launch," said Rick. Lu's mother watched the launch from mission control in Moscow.

Fred Gregory, deputy NASA administrator, who was present for the take-off along with other top US and Russian space officials, including Russian Space Agency chief Yuri Koptev, paid tribute to the Russians.

"I was very impressed with the people, the professionalism and the successful launch. It's my first time on Baiknour," he said.

"It has been quite an achievement with the Russians and Americans, they have done a magnificent job.

"This was a very, very important mission, that we have people going up. It shows the commitment of partnership to a continued sustained presence on the station," added Gregory.

Since NASA grounded the remaining three space shuttles after the Columbia accident, Russia's Soyuz manned craft and Progress cargo vessels have been the only means to transport crew and supplies up to the 16-nation space station.

Because of the problem of getting supplies to the ISS, which were mainly delivered by shuttles, missions to the space station will comprise two, instead of three, astronauts.

Lu and Malenchenko will be eagerly awaited by the current ISS crew, US astronauts Kenneth Bowersox, Donald Pettit and Russian cosmonaut Nikolai Budarin, who were to return in March but had to extend their mission after the Columbia tragedy.

After a week to hand over control of the orbiting space station, the outgoing crew will make the journey back to Earth on May 4. Lu and Malenchenko will be replaced by another two-man crew in October.

At the launch-pad in the barren, dusty Kazakh steppe, the two astronauts had climbed aboard the rocket-shaped Soyuz craft some two and a half hours before lift-off, hoisted to the hatch at the top on a hydraulic elevator.

Neither said anything but gave the thumbs-up. Under an old Soviet-era tradition that is supposed to bring luck, the astronauts urinate on the wheel of the bus which takes them to the launch site.

As dawn broke and a pale orange glow filled the sky, they headed off for their flight after a 45-minute meeting of a state commission that gave the fina! l go-ahead.

The astronauts, wearing white space suits, underwent last-minute tests as Russian space technicians pressurized their suits to test them for leaks.

The officials told the two-man crew that Russian President Vladimir Putin had telephoned to wish them a safe flight.

Lu and Malenchenko earlier checked out of the Cosmonaut Hotel just before 3 am local time with music blaring of a Soviet song "Earth through the porthole," a long-standing tradition in Baikonur.

A black-robed Orthodox priest holding a gold cross walked around their bus sprinkling it with holy water, on what is the eve of Easter in the Orthodox calendar. He had said a prayer and blessed the Soyuz rocket the day before.

SPACE.WIRE