A government statement said Prime Minister Rafiq Hariri summoned US ambassador Jeffrey Feltman to express his objections to the proposal on Saturday.
US Congressional aides briefed by the Bush administration said on Friday that the administration was considering applying further sanctions under the Syrian Accountability Act to step up pressure on Damascus, which has an estimated 14,000 to 17,000 troops in Lebanon.
A US administration official said a leading option under consideration was freezing the assets of high-ranking government officials.
"Prime Minister Rafiq Hariri summoned US ambassador Jeffrey Feltman today to express concern and opposition to a request by members of Congress to US President George Bush to freeze assets of Lebanese and Syrian officials to pressure Lebanon and Syria," Hariri's office said in a statement.
It quoted Feltman as saying the proposal was not yet law, but reflected "the very strong concern within the US Congress about supporting the sovereignty and independence of Lebanon".
Some US lawmakers said Bush did not go far enough and were pressing him to go further. They pointed to a report earlier this month by UN Secretary-General Kofi Annan, who said Syria had failed to meet a Security Council demand it withdraw its forces from Lebanon.
Syria keeps as many as 17,000
troops in Lebanon
Republican Representative Ileana Ros-Lehtinen of Florida, who chairs the House of Representatives International Relations subcommittee on Middle East affairs, wrote to Bush last week urging him to freeze the assets of those who contributed to Syria's military presence in Lebanon, where Damascus has had ultimate authority since the 1975-1990 civil war.
The US moves, and a US-backed UN Security Council resolution demanding foreign troops leave Lebanon, marked an increase in pressure on Damascus, accused by Washington of supporting Hizb Allah and failing to stop insurgents from entering Iraq.