HOUSTON (Reuters) – The United States on Friday targeted oil shipments from Venezuela to Cuba in its latest round of sanctions to pressure the government of President Nicolas Maduro, aiming to choke off a crucial supply of crude to the Communist island.

The U.S. Treasury imposed sanctions on 34 vessels owned or operated by Venezuelan state-run oil company Petróleos de Venezuela, S.A, or PDVSA , and also on two companies and a vessel that delivered oil to Cuba in February and March.

“Treasury is taking action against vessels and entities transporting oil, providing a lifeline to keep the illegitimate Maduro regime afloat,” said Treasury Secretary Steve Mnuchin in a statement.

“Cuba continues to profit from, and prop up, the illegitimate Maduro regime through oil-for-repression schemes as they attempt to keep Maduro in power.”

The latest round of U.S. sanctions, announced earlier by Vice President Mike Pence in a speech in Houston, aim to further undermine Maduro’s government after the United States and most Western nations recognised opposition leader Juan Guaido as the rightful president of Venezuela.

Guaido invoked the Venezuelan constitution to assume an interim presidency in January, arguing that Maduro’s 2018 re-election was illegitimate.