The stocks for pharmaceutical companies dropped in price on July 5 after President Donald Trump said his administration is working on an executive order which would require drug companies to price their medicines based on the lowest amount paid for the same drug by another nation.

SPDR S&P Pharmaceuticals, an exchange-traded fund tracking the stocks of major pharmaceutical companies, was down 1.5 percent at 1:10 p.m. on July 5. The index began declining immediately after Trump told reporters on the White House lawn about preparations for the executive order.

“We’re going to be announcing something very shortly, a favored nations clause. As you know, for years and years other nations paid less for drugs than we do. Sometimes by 60-70 percent. We’re working on it right now, we’re working on a favored nations clause, where we pay whatever the lowest nation’s price is. Why should other nations—like Canada—but why should other nations pay much less than us. They’ve taken advantage of the system for a long time, pharma,” Trump said.

“But we’re working on right now a favored nations clause, so that whatever the lowest nation is anywhere in the world, or company, but the lowest nation or company, then what happens is, we will pay that amount. And that’s being worked on right now. We’re gonna do it in the form of an executive order,” the president added.

In October last year, Trump announced a new rule that would bring the prices Medicare pays closer to what other countries pay and save taxpayers an estimated $17.5 billion over the next five years. The president unveiled the rule after the Department of Health and Human Services released a report on drug prices under Medicare Part B, which estimated the United States is paying on average almost two times what other countries are paying.

Trump has taken a number of other steps to lower drug prices. In January, the administration proposed a rule to cut out the middlemen and require drug companies to pay rebates directly to consumers. Every year, an estimated $150 billion is passed around the rebate system to middlemen like pharmacy benefit managers with consumers left entirely in the dark.

Another administration rule will require drug companies to list the prices for their medicine in television advertisements. Earlier this month, the president issued an executive order which, once implemented, would require hospitals to display prices for services upfront.

“When prices are transparent and competition is encouraged, consumers win. We believe that can prove true in health care as it has in every other area of the American economy,” Alex Azar, the secretary of Health and Human Services, wrote in an op-ed in February.