Maduro said he has evidence to back up his suspicions that former Colombian President Alvaro Uribe was trying to have him killed, likely with the help of U.S. operatives.
A representative of the U.S. Embassy in Caracas told The Wall Street Journal the allegations were without merit.
"The U.S. continues categorically to reject any allegations of U.S. government efforts to destabilize the Venezuelan government or to harm anyone in Venezuela," the unidentified diplomat said.
Maduro, a socialist who narrowly won the April 14 election to succeed the late Hugo Chavez, alleged Uribe "is behind a plan to assassinate me."
The conservative Uribe was a vocal opponent of Chavez's regime while he was president of Colombia from 2002-2010.
Uribe was not immediately reached for comment, the Journal said.