China's three astronauts spent their first day in orbit Friday preparing for a much-anticipated walk outside their craft, as Japan voiced hopes its giant neighbour had peaceful aims in space.

The voyage of the Shenzhou VII, China's third manned foray into space, has proceeded without a glitch since it blasted off from Jiuquan Satellite Launch Centre in northwest China late Thursday, state media said.

"We feel physically sound," the trio, led by Zhai Zhigang, reported back to ground control after blast-off, Xinhua news agency reported.

At 4:04 am (2004 GMT Thursday) the Shenzhou VII entered into a round orbit around Earth from its initial oval orbit, a complicated manoeuvre which makes it possible for the three to get down to the real business of the journey.

The astronauts spent most of the day assembling and testing the space suit that one of them -- most likely 41-year-old Zhai -- was to put on for an unprecedented walk in space scheduled for Saturday, Xinhua said.

Zhang Jianqi, one of the chief engineers for China's space programme, said keeping three men in the spacecraft, and then sending one outside, would be a "big test".

"This is a big technological leap," he told Xinhua. "The risks are quite high. Sending up three astronauts is a jump both in quantity and quality."

Space motion sickness can cause dizziness, vomiting and nausea, and in severe cases, astronauts might feel severe pain in the joints, have breathing difficulty or could even lose consciousness.

"Some of these can be life-threatening," said Li Yongzhi, director of the medical department of the China Astronaut Research and Training Center, according to the China Daily newspaper.

The Shenzhou VII mission -- coming just days before the 50th anniversary of the US National Aeronautics and Space Administration, or NASA, on October 1 -- was a potent symbol of the Asian power's emergence as a space power.

A Xinhua announcement Friday that the next generation of spacecraft, Shenzhou VIII, would be "mass produced" was likely to underline this message, and perhaps unnerve China's neighbours.

Japan congratulated China Friday on the mission, hinting that the two nations might work together in space in future.

"Perhaps we are reaching a moment in time where we may consider cooperating with China over space issues," said Chief Cabinet Secretary Takeo Kawamura. "But we hope that China will fulfill its role as a peaceful nation."

Japan has frequently voiced concerns about rapidly growing military spending in China, which last year carried out a test in which it shot down a satellite.

During their 68 hours in orbit, the three astronauts will be able to enjoy an unprecedented choice of food.

The menu includes spicy chicken with peanuts, shrimps and dry fruits -- 80 items in all, up from only 50-odd in China's last mission in space three years ago.

"We have tried to make them taste like stir-fried dishes they have on Earth," Chen Bin, who is in charge of food for the astronauts, told Xinhua.

In choosing food fit for space, Chen said he had avoided ingredients that produce gas after being digested, such as milk and soybean. "Meat and egg are better," he said.

Chinese state media has treated the journey as a major national triumph, coming just a month after the Olympics, but in at least one case got ahead of itself.

On Thursday morning -- hours ahead of blast-off -- Xinhua posted a story on its website reporting how the Shenzhou capsule was being successfully tracked high over the Pacific Ocean.

The story, dated September 27 and including supposed dialogue, was written from one of the numerous tracking ships China's space programme sends around the world to follow space flights.

It described in a vivid, blow-by-blow account how the spacecraft's signals were being monitored.

"Pressure in the cabin is normal. Oxygen pressure in the cabin is normal," an astronaut was quoted as reporting.

"There was a technical problem. We dealt with it after we had found it," an editor at Xinhua told AFP when asked about the story.

China sent its first man into space in 2003, followed by a two-man mission in 2005.

The Shenzhou VII is scheduled to land in the northern Inner Mongolia region after the mission is completed.