Cuba has wanted dissident Luis Posada Carriles for years
The US has denied that it is harbouring a Cuban exile accused by President Fidel Castro of plotting to kill him.
The top diplomat for Latin America said he did not even know if Luis Posada Carriles was in the US.
Mr Posada Carriles is also wanted in Venezuela over the bombing of a Cuban airliner in 1976, in which 73 people were killed. He has denied involvement.
He reportedly entered the US some weeks ago after months in hiding and was said to be seeking asylum there.
On Tuesday the Venezuelan Supreme Court ruled that Caracas should seek his extradition as he is a Venezuelan citizen.
“I don’t even know that he is in the United States,” state department official Roger Noriega said.
Cuban claims about Mr Posada Carriles “may be a completely manufactured issue”, he added.
Mr Posada Carriles once boasted of being responsible for a series of bomb attacks on Havana tourist spots in the 1990s.
Five years ago, he was arrested in Panama and accused of plotting to kill Mr Castro during a summit there.
He was convicted of a lesser charge, but was later pardoned and freed by the outgoing Panamanian president - causing Cuba to break off diplomatic relations.
He has been in hiding since then.