TOP United States Government officials have expressed concern over British concessions to China on Hong Kong's political reform package, according to legislator Martin Lee Chu-ming. On a trip to Washington, Mr Lee said officials wanted a full briefing on why the Patten proposals - which President Bill Clinton backed last summer - were likely to be watered down before going to Legco. The impressive array of top officials who met Mr Lee yesterday was a clear indication of Hong Kong's importance in US foreign policy. The United Democrats' chairman had separate meetings with Acting Secretary of State Peter Tarnoff, Assistant Secretary of State for Human Rights John Shattuck, Assistant Secretary of State for East Asian Affairs Winston Lord, and National Security Council policy chief Sandy Berger. Mr Lee also had talks with senior members of the Congress and Senate, who promised to closely follow the situation. Mr Lee said: ''I told them my concern was that if these amended proposals were kept, we would not have a legislature after 1997 which would preserve freedoms under the rule of law. The legislature would just be a rubber stamp.'' The officials stressed their support for more democracy in Hong Kong, and for the terms of the Joint Declaration, he said. Mr Shattuck said: ''Democratic participation was one of the pillars of President Clinton's foreign policy, and we certainly hope to secure a commitment to continued participation on the part of the Hong Kong citizens, and a protection of the basic rightsof Hong Kong citizens.'' US legislators also agreed in principle to set up a US-Hong Kong Parliamentary Friendship Group.