US President Donald Trump has said that his country will "run" Venezuela until a political transition can occur, after the unprecedented US military attacks to seize Venezuelan leader Nicolas Maduro and his wife Cilia Flores from the country.

"We're going to run the country until such time as we can do a safe, proper and judicious transition," Trump told a press conference on Saturday, adding that US forces were ready to conduct a second, "much bigger" wave of strikes if necessary.

Giving details of the US attacks, Trump said the US military caused a blackout in the Venezuelan capital Caracas so it could carry out an operation to seize Maduro.

"It was dark. The lights of Caracas were largely turned off due to a certain expertise that we have," Trump told media at his Mar-a-Lago resort.

"This was one of the most stunning, effective and powerful displays of American military might and competence in American history," Trump added.

He said US air, land and sea forces were used in the operation.

US eying Venezuela’s oil

Venezuela has the world's largest oil reserves but its crude output remains at a fraction of capacity due to lack of investment and US sanctions, official data shows.

Venezuela holds about 17 percent of global reserves or 303 billion barrels, ahead of Organization of the Petroleum Exporting Countries leader Saudi Arabia, according to the London-based Energy Institute.

Its reserves are made up mostly of heavy oil in the Orinoco region of central Venezuela, making its crude expensive to produce, but technically relatively simple, according to the US government's energy department.

Trump told media that US oil firms will now head into Venezuela.

"We are going to have our large oil companies go into Venezuela," the US leader said.