China launched a three-man crew into space Thursday night, including one who will make the country’s first spacewalk — its most challenging mission since its first orbital flight in 2003.

The Shenzhou 7 spacecraft, China’s third manned mission, blasted off atop a Long March 2F rocket into a clear night sky in northwestern China.

Hours later, the spacecraft moved into a round orbit 213 miles above earth, the official Xinhua News Agency reported. The three astronauts — who were reported in good physical condition, with body temperature and blood pressure normal early today — were scheduled to assemble and test their space suits later in the day ahead of the spacewalk, which Xinhua said will most likely happen on Saturday afternoon.

China Manned Space Engineering Office said earlier that the spacewalk could occur either today or Saturday, depending on how well the astronauts adapt to weightlessness and other physical demands of their environment.

Underscoring the mission’s weighty political overtones, President Hu Jintao was shown live on state television before blastoff praising the crew at the launch site near the northwestern town of Jiuquan.

“You will definitely accomplish this glorious and sacred mission. The motherland and the people are looking forward to your triumphant return,” Hu told the three, who were dressed in their flight suits and stood behind glass to avoid germs.

The launch was carried live on state television in a display of China’s growing confidence in the 16-year manned space program. Shortly before the transmission ended, one of the crew reported in that all were in good condition and had extended the three-module spacecraft’s solar panels.

Today’s maneuver to a round orbit was necessary to ensure smooth operation of the ship and a precise landing when its re-entry vehicle bursts through the earth’s atmosphere to settle on the steppe in Inner Mongolia, Xinhua said.

It came at 4:03 a.m. when the astronauts executed a 64-second burn to shift the spaceship from an oval-shaped orbit in which its distance from earth varied into a round one in which the distance was constant, Xinhua reported.

The mission, expected to last three to four days, is devoted almost entirely to the spacewalk. The event is expected to help China master the technology for docking two orbiters to create China’s first space station in the next few years.

The two astronauts who don spacesuits for the Shenzhou 7 spacewalk will be supported by Russian experts throughout the mission. Only one will actually leave the orbiter to retrieve scientific experiments placed outside. One of the astronauts will wear China’s homemade Feitian suit, while the other will wear a Russian-made suit.