VIETNAM may try to limit international access to its vast Mekong delta under a new United Nations-brokered agreement for joint development of the river. With the first committee meeting of the Mekong Commission just weeks away, Vietnam is seeking talks with fellow member Cambodia on limiting free navigation to just one branch of the Mekong. Senior Vietnamese rivers official Hoang Trong Quang said the agreement on the Co-operation for Sustainable Development of the Mekong River Basin stipulated free navigation on only the main stream of the river. Despite previous navigational flare-ups, Cambodian ships ply both the Mekong and its wider tributary, the Bassac, to move goods to Phnom Penh. 'It's going to have to be one of the first things to be sorted out,' said Mr Quang, permanent secretary of the Vietnam National Mekong Committee. 'The agreement makes it clear that free navigation is limited to the main stream, so we've got to sort out which one of the routes to Phnom Penh will be used by international ships,' he said. Ships from all over the world call at Can Tho on the Bassac, a trading centre in the delta, which produces more than half of all Vietnam's rice and nearly a third of its gross domestic product. Navigational rights were hammered out in December last year after Vietnam impounded several Cambodia-bound freighters on the Mekong, accusing them of carrying banned goods in the midst of frosty relations between Hanoi and Phnom Penh. The issue will be one of the first tests of the joint agreement, which created a new Mekong Commission between Thailand, Laos, Vietnam and Cambodia in April after months of negotiations led by the UN Development Programme. In essence, the deal requires full agreement from all members on any development that would upset the dry-season flow of the 4,200-kilometre Mekong - the longest un-dammed river on earth. The agreement, which is enforceable in international courts, also carries a string of co-operation pledges on the environment and water quality. Mr Quang said the Mekong was vital to Vietnam and the country was committed to the peaceful implementation of the agreement, which could break new ground in protection and co-operation on sensible development. The South China Morning Post has learnt that China and Burma will be invited to join the commission soon, with diplomatic sources saying all four signatories had already agreed to try to bring them in as soon as possible. China is reportedly considering damming the upper reaches of the river in Yunnan, a move which, under the agreement, would have to be put to the Mekong Commission. Thailand, Laos and Cambodia are also investigating a range of projects which may need to be put before the commission. However, before any firm proposals are examined, China's and Burma's inclusion must be dealt with along with the thorny question of where to base the commission's headquarters.