Caracas, Venezuela (CNN) -- Venezuelan President Hugo Chavez said authorities have arrested a U.S. citizen who "had all the appearances of a mercenary" working to destabilize the South American country's government.
"We are interrogating him," Chavez said at a campaign event Thursday.
Chavez said the man, whom he did not identify, was arrested five days earlier while illegally trying to cross the border from Colombia into Venezuela.
U.S. officials are operating on the assumption that Chavez's forces have someone in custody, a U.S. government source told CNN on Friday. U.S. officials have reached out to the Venezuelan government on the matter, but haven't received information, the source said.
Chavez said the passport the man was carrying had stamps from recent years in Iraq, Afghanistan and Libya. The president also said police seized a notebook with written coordinates from the man.
"It sends a powerful signal, how this citizen wanted to illegally enter the country, to do who knows what. ... He says he was fleeing from I don't know who. The certainty is that this forces us to activate many more alarms everywhere," Chavez said.
Chavez, who is running for reelection, has repeatedly accused U.S. officials and members of Venezuela's opposition of plotting to destabilize the country's government.