UNITED States diplomats are seeking greater access to two Vietnamese-American men jailed for their role in an outlawed political movement working to overthrow Hanoi's leadership. Nguyen Tan Tri, Nguyen Quang Liem and seven others associated with the Tan Dai Viet Party were sentenced at the weekend. The party has been banned since the communists took Saigon in 1975. The US State Department has previously raised concerns over the pair's detention, but Vietnam's state press said they had been found guilty of 'very serious violations of national sovereignty and security'. Officials at the new US Embassy want Hanoi to grant them the right to make ongoing visits to Tri and Liem in jail. They were given just 24 hours' notice of the trial. But agreements on the handling of prisoners between Washington and Hanoi do not stipulate the right to repeatedly visit prisoners or the length of notice which should be given for a trial. US officials stood by at the trial but have yet to visit the pair after sentencing. The sentences came less than a week after the historic visit to Hanoi of US Secretary of State Warren Christopher, during which he called for a more open economic and political system. The pair were arrested nearly two years ago as the group planned to stage what Vietnam's state press yesterday described as an 'international workshop' on the country's development. The workshop had been poised to create a party executive with the 'notorious Saigon reactionary' Nguyen Dinh Huy at its head. Huy had drafted the year before a manifesto for the Movement for National Unification and Democracy, which official reports have warned could work for the overthrow of Communist Party rule with backing from abroad. The party remains in exile in California and Huy had kept contacts with the group while in re-education in 1990. Huy was sentenced to 15 years while others in the group received four-and seven-year sentences. The two Americans will be deported after serving their time and will be barred from returning to Vietnam for up to five years. The sentencing comes as the head of Vietnam's internal security insisted his forces were strong enough to cope with 'enemies of the country'. In a rare address to celebrate the 50th anniversary of the Vietnamese police force, Interior Minister Bui Thien Ngo said his officers must show 'absolute loyalty to the revolutionary cause of the party and people'. Prime Minister Vo Van Kiet had said Vietnam had to open its doors to ensure it would not fall behind other countries but 'at the same time we must know how to defend ourselves and maintain our identity'. A leader of the dissident United Buddhist Church of Vietnam and five followers who organised a flood relief mission are to be tried for public order violations, an official said yesterday. Thich Quang Do, secretary-general of the church, three other monks and two lay Buddhists will face a closed trial beginning today.