Venezuela's foreign minister on Monday blasted her U.S. counterpart John Kerry for questioning the country's democratic credentials ahead of legislative elections the ruling socialists are forecast to lose.

The spat follows a nascent rapprochement earlier this year between the two ideologically-opposed nations.

In an interview broadcast by CNN en Espanol on Monday, Kerry described Venezuela as "troubled" 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, Foreign Minister Delcy Rodriguez said Venezuela rejected Kerry's comments."The electoral register in the United States is founded on discrimination... Our political system is founded on democracy."

Venezuela and the United States have had difficult relations since late president Hugo Chavez was elected in 1998.

They came to a nadir in 2006 when Chavez described his then U.S. counterpart George W. Bush as "the devil."

The two countries have not had ambassadorial ties since 2010.

On Sunday, Venezuela's President Nicolas Maduro said President Barack Obama was delaying consent for his proposed new ambassador in Washington.

The United States has not named a proposed ambassador to Venezuela and U.S. officials in Caracas did not immediately respond to requests for comment.

Relations began to warm earlier this year though the process appears to have been set back when Leopoldo Lopez, a jailed opposition leader, was sentenced to nearly 14 years in prison in September on charges of fomenting anti-government violence.

Washington had been pressing for Lopez's release.