WASHINGTON, United States (AFP)—The United States on Thursday announced sanctions against Cuba’s key state-owned oil company, intensifying pressure on the island nation’s energy sector that has crippled the country.

“Today, I am designating Cuba’s state-owned oil and gas company Union Cuba-Petroleo (CUPET), key assets of which were unlawfully expropriated from American owners years ago,” US Secretary of State Marco Rubio said in a statement.

The move bars companies and individuals associated with the United States from engaging in any financial transactions with CUPET, which controls extraction at Cuban crude oil fields as well as refining and distribution.

Cuba’s government said on Wednesday the US oil blockade that has crippled the island is preventing the United Nations from distributing 170 containers of humanitarian aid.

US President Donald Trump in January cut off oil supplies to Cuba from its main supplier Venezuela, after Washington deposed the Venezuela’s then president Nicolas Maduro in a military operation.

Trump says he wants to end more than six decades of communist rule in Cuba, and has threatened other countries with sanctions if they come to the country’s aid.

Since January, only one oil tanker — from Russia — has made it through.

The blockade, coupled with expanded US sanctions that punish companies doing business with the Cuban state, has intensified the worst economic and energy crisis on the island in over a generation.

Parts of Havana have been without power for up to 30 hours at a time in recent days, and food, running water and medicine are in increasingly short supply.

Trump claims that Cuba, which lies 150 kilometers (93 miles) off Florida’s coast, poses a major threat to US national security and has suggested Washington could launch a “takeover” of the island of 9.6 million people.