Chavez said Venezuelan officials have intelligence that associates of jailed Cuban anti-communist militant Luis Posada Carriles also are involved in plotting to assassinate him.
He said the death plot idea has "gained weight" due to various factors, including the recent appointment of Negroponte, the former director of national intelligence, as deputy to Secretary of State Condoleezza Rice.
"Who did they swear in ... there at the White House as deputy secretary of state? A professional killer: John Negroponte," Chavez said.
Chavez did not elaborate, but his government has previously accused Negroponte of playing a key role in the Contra war against the leftist Sandinista government of Nicaragua when he served as ambassador to Honduras — a haven for clandestine Contra bases — from 1981 to 1985.
U.S. Embassy officials could not immediately be reached for comment, but they have denied Chavez's repeated accusations that they are plotting to oust him.
Chavez was asked about reports of assassination plots during a televised interview.
"They have assigned special units of the CIA, true assassins, who go around not only here in Venezuela, in Central America, in South America," Chavez said, without elaborating.
He added that while Posada Carriles, a former CIA operative, remains jailed in the U.S. on immigration charges, "Posada Carriles' people are very active in Central America and searching for contacts in Venezuela ... They are going around searching for explosives in large quantities, thinking about a sort of car bombing or searching for ground-to-air missiles, thinking about the presidential plane."
Chavez did not give details. His government has demanded that the U.S. extradite Posada Carriles, a naturalized Venezuelan, to stand trial for allegedly masterminding the 1976 bombing of a Cuban airliner that killed 73 people. Posada Carriles denies involvement in that incident.