WASHINGTON (Reuters) - The United States imposed new sanctions on six Venezuelan security officials and revoked the visas of dozens of associates and their families with ties to President Nicolas Maduro, in the latest move to pile pressure on him to step down.

The U.S. Treasury said the six current or former security officials controlled groups that blocked humanitarian aid from reaching people in Venezuela last weekend from neighboring countries Colombia and Brazil.

“We are sanctioning members of Maduro’s security forces in response to the reprehensible violence, tragic deaths, and unconscionable torching of food and medicine destined for sick and starving Venezuelans,” U.S. Treasury Secretary Steven Mnuchin said.

The United States “will continue to target Maduro loyalists prolonging the suffering of the victims of this man-made humanitarian crisis,” Mnuchin added.

Separately, the U.S. envoy for Venezuela, Elliott Abrams, said the United States had revoked visas of “dozens more” Venezuelans, although declined to elaborate, saying U.S. laws prevented him from discussing details about visas.

“We continue to look at close associates of Maduro, who with their families have visas to the United States,” Abrams said at a news conference.

Friday’s action is the second set of sanctions by the United States this week. On Monday, Washington targeted four Venezuelan state governors allied with Maduro and called on allies to freeze the assets of state-owned oil company PDVSA.

U.S. sanctions block any assets the individuals control in the United States and bars U.S. entities from doing any business or financial transactions with them.

The Trump administration and dozens of other countries have recognized opposition lawmaker Juan Guaido as Venezuela’s interim president. Guaido, head of Venezuela’s National Assembly, has invoked constitutional provisions to assume an interim presidency, arguing that Maduro’s re-election last year was fraudulent. Guaido has since been recognized by most Western nations as the rightful leader of Venezuela.

Maduro still controls the military, state institutions and oil company Petroleos de Venezuela SA, which provides 90 percent of the country’s export revenue.

Russia has accused the United States of preparing to intervene militarily in Venezuela and this week, along with China, blocked a U.S. bid to get the U.N. Security Council to take action on Venezuela.

Abrams said he was in talks with Russia on Venezuela. Both Moscow and Beijing were unlikely to provide additional financial support to Maduro’s government although they continued to give him diplomatic and political cover, he said.

“We have made the argument, unsuccessfully to date, to both Russia and China that they are not helping themselves,” Abrams said. “If they are concerned ... about the recovery of money they have lent or invested, a bankrupt Venezuelan economy will never be able to repay those amounts, only a Venezuela in recovery will be able to do so.”