Caracas (AFP) - Tighter new US sanctions against Venezuela are aimed to foment violent unrest to try to overthrow President Nicolas Maduro, his defense minister said Saturday.

"This US interference is aimed at promoting violence... against our institutions" to oust staunch US critic Maduro, Defense Minister Vladimir Padrino told Telesur television.

US President Barack Obama signed a law on Thursday to allow sanctions against senior Venezuelan officials accused of violating the rights of protesters during anti-government demonstrations that rocked the country earlier this year.

The text approved just over a week ago by both houses of the US Congress would freeze assets and deny visas to Venezuelan authorities responsible for violence and political detentions triggered by the protests.

Thousands of activists were arrested and more than 43 people were killed during mass demonstrations that raged from February to May against the government of Maduro, the elected successor of late leftist firebrand president Hugo Chavez.

Maduro has repeatedly accused the United States of fomenting the protests and seeking to overthrow and even assassinate him.

The Venezuelan leader condemned the sanctions law in a series of Twitter posts this week, calling it a "misstep" that resembled the US policy isolating Cuba, which was overturned Wednesday as Obama and Cuba's leader Raul Castro announced a bilateral rapprochement.

"The background of all this is much more nuanced. It is dangerous because these are the steps they are taking so that they can try to have the world see the Venezuelan state as a failed one," Padrino warned.

Caracas and Washington have had strained diplomatic ties since Chavez first came to power in 1999, leading to the withdrawal of ambassadors from each other's countries in 2010.

Still, the United States is the main buyer of Venezuelan oil.