The US will control sales of sanctioned Venezuelan oil "indefinitely" as it prepares to roll back restrictions on the country's crude in global markets, the White House said.

Officials said sales were expected to start with 30 million to 50 million barrels of oil and the revenue would be controlled by the US government in order to maintain leverage over the Venezuelan government.

"We're going to let the oil flow," Energy Secretary Chris Wright said at a conference with energy executives in Miami.

It's not clear what portion of the revenues from the sale - which analysts expect to raise about $2.8bn (£2.1bn) - would be shared with Venezuela.

"We need to have that leverage and control of those oil sales to drive the changes that simply must happen in Venezuela," Wright said, while adding that some of the money would then "flow back into Venezuela".