Liu Xiang has come back strong, but his opponents won't allow him an easy path to glory in London, the Chinese track and field team's head coach warned.

After winning three consecutive outdoor events in world-class times, Liu has shown he has fully recovered from his foot injury and is a hot favorite for the Olympic gold medal in the 110 meter hurdles.

The 28-year-old beat major rivals, including the United States' reigning world champion Jason Richardson and 60m indoor world champion Aries Merritt, with fine performances at the Japan Grand Prix, the IAAF Diamond League's Shanghai and Eugene, Oregon, meets in recent times.

Still, his ascent to the top of the podium in London will be tough and long, said Feng Shuyong, head coach of the Chinese athletics team.

Feng hopes Liu can deliver at least a medal at the Games, but remains wary of his foreign opponents.

"A lot of people think Liu will have no problems in winning in London because all of his major opponents have not performed as well as him (this season)," Feng said. "But that is not true."

"Other contenders, especially the Americans, didn't hit their top form until their Olympic trials. They had a lot of races over the past two months, they were tired and they didn't prepare as well as Liu did."

At the Eugene meet last month, Liu edged out Richardson and Merritt with a world-record-tying time of 12.87 sec on their home soil, and regained the world No 1 spot for the first time in five years.

Despite a strong tailwind costing him a share of the record — held by Cuba's Dayron Robles — Liu stunned the world with his quick return to the top.

However, Feng has said Liu must remain wary of the Americans.

"They were not at their best, so you can't make judgments based on their performances at that time. They will catch up and become dangerous again," Feng said.

Indoor 60m world champion Merritt surpassed Liu's previous season best of 12.97, achieved at the Shanghai meet in May, to win the 110m hurdles in 12.93 at the US trials.

The current world-record holder and defending Olympic champion Robles did not appear in Eugene or at a meet in New York due to visa and injury problems.

Without any great exposure on the international stage this season, Robles remains somewhat of an enigma. Liu and the Cuban have not raced each other outdoors since last year's Worlds in Daegu, South Korea.

At an indoor meet in Birmingham in February, Liu outperformed Robles by 0.09 to win in 7.41.

Robles, 26, is battling several injuries, but Feng said he remains an "extremely dangerous" threat to Liu.

"He is still young and he is the man who has run under 13 seconds the most times. We can't say he's not coming back right now."

Liu's recent red-hot form has also caused some concern that he may have peaked too early. Feng does not appear too worried.

"I don't think that (the concern) makes sense," he said. It's a natural reflection of his training. He works hard and steady. He runs smoothly without mistakes. It's where he should be, but not at the top yet."

Apart from Liu, women's discus thrower Li Yanfeng has emerged as another gold hope for China after winning the country's only title at the Worlds last year.

The 33-year-old Li will join Liu to lead a 53-strong squad to compete in 28 different events at the track and field competition in London from Aug 3-12.

Feng said the team would aim to produce medals in eight events, including women's marathon, shot put and hammer as well as the men's race walk.

"Chinese athletes have a chance to win medals in these events. But nothing will be taken for granted," said Feng.

China dominated the medal table at the Beijing Olympics with an overwhelming 51 gold, but failed to pocket any in track and field.