Chinese artist Ai Weiwei said Friday on a rare sojourn in London that Chinese officials may be loosening their attitudes toward him, but he has some concerns about his planned return to his homeland in several weeks.

The prominent dissident said the fact that the Chinese government allowed him to travel to Germany, where his young son lives, and to Britain, where a major exhibition of his works opens next week, indicates more acceptance of his work. He said he has been assured he will be allowed to re-enter China.

"We'll find out," Ai said at a press conference to mark his upcoming show at the Royal Academy of Arts. He admitted he has "no idea" whether he will encounter any difficulties.

Ai, who has been incarcerated in the past and had his passport seized for more than four years, said the Chinese placed no conditions on his departure for Europe.

He said he hopes to be able to divide his time between Berlin, where he plans to teach at the University of the Arts, and Beijing, where he has his studio and artistic base.

Ai said that until now he had repeatedly been disappointed in his efforts to travel because officials never followed up on promises to return his passport.

He said officials told him he was being punished for "subversion of state power."

Asked if that attitude has now changed, Ai said: "It's hard to measure. In my case it's improved or I wouldn't be here."

He pointed out, however, that his lawyer remains in detention in China.

Ai said that when he is in China he is in frequent communication with police who contact him once a week or more via phone or text message.

He said his time in prison had been very difficult for his son — "He had nightmares, he told me 'Daddy, they'll never let you go'" — and for his elderly mother.

Ai seems to be enjoying the late summer in London as he and curators put the final touches on a major retrospective of his work since 1993.

"It's so comfortable," he said. "You can breathe the fresh air and see the light of London. It's new."