A demonstrator holds a placard as she takes part in a protest of Venezuelans against the government of President Nicolas Maduro at the Simon Bolivar International bridge in Cucuta, Colombia, on the border with Venezuela, on February 15, 2019.

The U.S. is adding six high-ranking Venezuelan security officials on its international sanctions list as it steps up pressure on the government of President Nicolas Maduro.

The six include officials with the National Guard and police blamed for their roles in blocking humanitarian aid convoys into Venezuela. They were announced by the Treasury Department on Friday.

The sanctions freeze any assets the people may have under U.S. jurisdiction and prevent anyone in the U.S. from conducting financial transactions with them.

It's part of a campaign to pressure Maduro to step down and turn over power to opposition leader Juan Guaido.

The U.S. recognized Guaido as interim president last month. Maduro was re-elected last year in an election widely viewed as illegitimate, but the security services have remained loyal.