By Greg Morsbach
BBC News, Caracas
Washington says the Venezuelan authorities have illegally seized and searched a diplomatic bag destined for the US embassy in Caracas.
Venezuela under Hugo Chavez has turned away from the US
The Venezuelan authorities say they were looking for military hardware being flown in illegally from the US.
But an embassy spokesman said this was nonsense and a serious violation of international rules.
The US state department has made a formal complaint to the government, demanding the bag be returned to them.
Venezuela's foreign ministry told the BBC that a piece of luggage belonging to the US naval attache had been seized but they stressed it was not, as it were, an official diplomatic bag.
A ministry official said they were alerted to three lorries leaving the airport compound without reporting to customs as required by law.
She said the third lorry was told to stop and that is when the military attache's belongings were searched.
Earlier this year, the government ordered the previous US naval attache to leave the country on suspicion of spying.
This appears to be a difficult start for his successor who has only recently taken up his job in Caracas.
Relations between Washington and Caracas are likely to be soured further by this episode.
Venezuela accuses the Americans of not respecting its sovereignty while the US views the government of President Hugo Chavez with growing suspicion.