VIETNAM yesterday moved to support the continued return of boat people under present international agreements now under threat by a bill before Congress in Washington. Breaking Hanoi's silence on the Washington situation, a Foreign Ministry spokesman said Vietnam called for all participants of the Comprehensive Plan of Action to make 'effective contributions' to the final settlement. 'Vietnam's constant policy is to closely co-operate with the United Nations High Commissioner for Refugees [UNHCR] and other concerned parties in the . . . repatriation of Vietnamese boat people who are now living in Hong Kong and elsewhere in Southeast Asia. 'Vietnam calls for the participants . . . to have effective contributions to the implementation of the programme.' The spokesman added: 'The regulations for classifying the screening of refugees under the Comprehensive Plan of Action is completely based on standards of international conventions . . . adopted in Geneva in 1951.' Yesterday's statement was Hanoi's first official comment on the bill, coming as leaders seek urgent restoration of full ties with Washington to cement Vietnam's return to the world stage. The ministry has yet to comment, however, on reports in yesterday's South China Morning Post revealing that Hanoi's Interior Ministry had shelved upcoming voluntary returns from the territory following a bureaucratic hiccup with the UNHCR. UNHCR officials fear the indefinite postponement of flights for more than 400 people this month adds more pressure to a programme under threat from Washington.