By Will Grant
BBC News, Caracas
Hugo Chavez made the comments on his weekly TV programme
Venezuela's President Hugo Chavez has insulted Colombia's defence minister over comments critical of the country's anti-drug trafficking efforts.
In his weekly TV programme, Mr Chavez said that Gabriel Silva must be "mentally retarded".
Last week, Mr Silva released a statement accusing Venezuela of failing to tackle international drug routes.
He said there was "almost a free traffic" of flights loaded with drugs from Venezuelan territory.
The bad feeling between the Venezuelan and the Colombian governments has been kept under control by a mutual silence for several weeks now, but it only takes a small event for it to erupt into insults again.
In this instance, the Colombian defence minister's comments were more than enough.
On his Alo Presidente programme, Mr Chavez gave a typically damning response.
"The Colombian defence minister? I think he's mentally retarded," he said.
He added that the only explanation for his behaviour was that he was "following instructions from the empire", referring to the US.
The president's comments come shortly after an official protest note was sent to Colombia by the Venezuelan foreign ministry.
But many commentators in Venezuela and Colombia say that such measured diplomacy is what is missing from this confrontation.
Mr Silva is due to head to meet US Defence Secretary Robert Gates in Washington shortly.
This latest outburst by Washington's most vocal critic in Latin America comes at a sensitive time over the US military's use of seven military bases on Colombian soil - something they say will help in the fight against drug trafficking, but which Mr Chavez says will destabilise the security of the region.