A US inventor who was prevented from leaving China for nearly five years in a row over trade secrets has been allowed home, Beijing said Wednesday, ahead of a presidential summit between the two powers.

Hu Zhicheng, a Chinese-born US national, arrived in California on Monday evening, reports in the US say.

The inventor, who spent 17 months in prison and was released three years ago after charges were dropped, had an emotional reunion with his family after legal restrictions on him leaving China were lifted.

"What I can confirm is that the restriction measures taken by the Chinese judicial authorities against him leaving the country has been revoked according to law," China's foreign ministry spokesman Hong Lei said.

Hu, one of the world's leading experts in catalytic converters, was accused of stealing information relating to automobile emission control technology.

During his time in custody he was held in a group cell in a detention centre in the northern coastal city of Tianjin.

After being released, Hu said that airport border control agents blocked his exit when he tried to leave China.

US President Barack Obama will meet with Chinese leader Xi Jinping on Friday and Saturday in California.