Presidential elections in November could also play a role, says Robert Rountree, chief East Asian strategist at Nomura Research Institute in Hong Kong.

CNN: A PUNTER'S SURVIVAL GUIDE

Denis Hew, of Singapore's Institute of South-East Asian Studies, blames the low uptake on several factors.

ECONOMIST: Free trade in South-East Asia

"Chinese Strategic, Economic and Social View of Vietnam", edited by Gu Xiaosong and Sheng Lijun, Institute for South-East Asian Studies, Singapore, 2005.

ECONOMIST: Sources and acknowledgments

David Koh, a Vietnam expert at Singapore's Institute for South-East Asian studies, says some degree of political liberalisation is being considered, though perhaps not as much as the West would like.

ECONOMIST: How long can the party last?