President Donald Trump has put a number on how much he wants the biggest US and European oil giants to pour into Venezuela: at least $100 billion.

During a meeting at the White House on Friday afternoon, oil executives made it clear that they were not yet prepared to follow through.

Darren Woods, who leads the largest US oil company, Exxon Mobil, was especially blunt during a televised portion of the meeting.

"We've had our assets seized there twice, and so you can imagine to re-enter a third time would require some pretty significant changes," he said. "Today it's uninvestable."

For the company to return to Venezuela, legal changes would have to be made, and there would need to be "durable investment protections", Woods, Exxon's chief executive, said. But he offered an olive branch to the White House, saying Exxon was prepared to send an exploratory team to Venezuela within the next few weeks if it received security guarantees.

Exxon and ConocoPhillips, another large American oil company, have been pursuing substantial claims against Venezuela's government for assets it seized during a nationalisation wave two decades ago.

Recouping that money seemed on Friday to be of little interest to Trump, who said, "We're not going to look at what people lost in the past, because that was their fault." He suggested the $12 billion in claims that ConocoPhillips has been pursuing might make a good write-off, a term for when companies recognise losses in a way that lowers their taxable income.

"It's already been written off," Ryan Lance, the company's chief executive, said in response to Trump.

Accounting rules require companies to generally write off investments that they are unlikely to make back, but that doesn't mean businesses have given up trying to recover that money. Many companies and investors spend years in court and arbitration cases in pursuit of money they are owed.

Some smaller businesses have been clamouring to establish or expand oil production in Venezuela, and energy trading or refining businesses would be happy to have more of Venezuela's oil flow to the US.

But even Harold Hamm, an Oklahoma oil tycoon and one of Trump's closest oil-industry allies, stopped short of committing to work in the country.

"It excites me as an explorationist. Everybody has that in their blood," Hamm said at the White House. But, he added, Venezuela has "got its challenges".

New York Times News Service