June 27, 2002 Posted: 6:43 PM HKT (1043 GMT)

(CNN) -- American Sinologist Perry Link says there has been a deterioration in the freedom of expression in Hong Kong and the situation could get much worse if an anti-subversion law is introduced.

Link, a world-renowned China expert and co-editor of the best-selling Tiananmen Papers, was detained for 45 minutes by Hong Kong immigration Wednesday before he was allowed in.

Speaking at the Hong Kong Foreign Correspondents' Club Thursday, Link said it was possible state security authorities in Beijing wanted to extend their regime of control to Hong Kong.

He added another, perhaps more probable reason could be anxiety on the part of the authorities of the Special Administration Region (SAR) of Hong Kong to ensure that no "troublemaker" would be in town during the upcoming visit of Chinese President Jiang Zemin.

Jiang is due in Hong Kong Sunday to celebrate the fifth anniversary of Chinese rule -- and Hong Kong immigration and police have also turned away a number of overseas Falun Gong practitioners in the run-up to the occasion.