Venezuelan Foreign Minister Delcy Rodrigez scolded her US counterpart John Kerry for questioning her country's democratic credentials for coming elections for which the ruling socialists are forecast to lose.
Kerry described Venezuela as "troubled" in an interview broadcast on Monday and said December's elections would be a "measure of the type of democracy that exists in the country."
Responding on Twitter on Monday night, Rodriguez said Venezuela can not accept Kerry's comments saying "The electoral register in the United States is founded on discrimination... Our political system is founded on democracy."
Venezuela and the United States have not had ambassadorial ties since 2010 and have had tough relations since late president Hugo Chavez came to power in 1998.
The relations deteriorated when Chavez described his then US counterpart George W. Bush as "the devil" in 2006.
Although relations began to warm earlier this year, they've had a set back when Leopoldo Lopez, an opposition leader in jail, was sentenced to 14 years in prison in September on charges of instigating anti-government violence.
USA had been insisting for the release of Lopez.
Venezuelan President Nicolas Maduro said on Sunday that President Barack Obama was delaying consent for his proposed new ambassador to Washington while the US is yet to name a diplomat for Caracas.