President Donald Trump wants to reverse the decades-long decline in the number of US refineries in operation, which he believes is key to lowering gas prices, and he recently called oil executives to the White House to make that push.

“President Trump and his entire energy team will continue supporting reopening shuttered refineries, expanding the capacity of existing refineries, and constructing new refineries to lower prices and strengthen our national security,” White House spokesperson Taylor Rogers told CNN.

But more US refineries won’t bring down prices in the near term and aren’t likely to take place in the long term either.

A new oil refinery with significant unit capacity hasn’t been built in America since 1977, and there were about twice as many oil refineries operating in 1982 as there are today. And even if a building boom were to start tomorrow, it would take years to produce the gasoline and diesel needed to alleviate current prices.

American oil companies, meanwhile, aren’t exactly rushing to build refineries. While the industry is wildly profitable, it’s also aware that the current energy market disruptions are temporary.