Rice, in an interview with the Lebanese Broadcasting Corporation, said Washington had received information of plots against the government of Prime Minister Fuad Siniora and other anti-Syrian forces in Lebanon.
"We too have heard that there are people who would like to destabilise the government of Prime Minister Siniora," Rice said, according to a transcript of the interview which was released by the State Department late on Monday.
"We've heard that there are people who would like to intimidate or assassinate again, they've done it before in Lebanon," Rice said, referring to the 2005 murder of former prime minister Rafiq Hariri in a giant car bombing in Beirut.
"The evidence is there that foreign influences have -- ever since the assassination of the former prime minister Rafiq Hariri -- have tried to use assassination and intimidation against the Lebanese people," she said.
While insisting she didn't want to accuse anyone specifically of threatening new attacks on Lebanese authorities, Rice added: "It's not any great secret that there are concerns about what Syria, which once occupied the country, might try and do through continuing contacts in the country."
"I don't want to accuse any one place; I just want to make very clear that the international community believes there should be no foreign intimidation of the Lebanese people," she said in the interview, which was conducted late last week.
Rice meanwhile met Monday with Lebanon's Druze leader Walid Jumblatt, a leading figure in the anti-Syrian movement, who was seeking US backing for the creation of an international court to try those found responsible for Hariri's assassination.
Hariri was assassinated on February 14, 2005 in a massive bomb blast on the Beirut seafront that killed 22 others. The popular five-time prime minister had opposed the three-year extension of the mandate of Lebanon's pro-Syrian president, Emil Lahoud.
Belgian prosecutor Serge Brammertz, who heads a UN inquiry into the murder, has pointed to possible links between Hariri's death and 14 other attacks against anti-Syrian personalities in Lebanon since October 1, 2004.
Syria has steadfastly denied any responsibility for the killings, but has come under heavy international pressure to co-operate with the investigations.
An international outcry over the murder of Hariri forced Syria, which had dominated Lebanese politics for three decades, to withdraw its troops from Lebanon in April 2005.
Since then, relations between the two neighbouring countries have soured considerably, and leaders of the anti-Syrian majority that emerged in parliamentary elections two months later have repeatedly claimed they fear for their lives.

Copyright AFP (Agence France-Presse), 2006