WASHINGTON (AP) — On Monday, President Donald Trump signed an order telling drug companies they have 30 days to lower the prices of their medicines in the U.S. voluntarily. If they do not, the government will set new limits on how much it will pay later.

The order tells the health department, run by Robert F. Kennedy Jr., to agree on new prices for medicines next month. If they don't make deals, Kennedy will have to create a new rule. This rule will link the price the U.S. pays for drugs to the lower prices paid by other countries.

Trump said on Monday that everyone would pay the same amount, like in Europe.

It's not clear how the Republican president's order will affect the millions of Americans who have private health insurance. The government has the most power to decide the price it pays for drugs under Medicare and Medicaid.

Trump said he would lower drug prices, but it's not certain this will happen. This came just hours after the Republican-controlled House shared their plan to reduce Medicaid funding by $880 billion.

The group for the main American drug companies quickly disagreed with Trump's order. They said it was not good for patients in the US. These companies have often said that if their profits are threatened, it could affect the research they do to create new medicines.

Stephen J. Ubl, the head of PhRMA, stated that using drug prices from socialist countries would be harmful to American patients and workers. He added that it would result in fewer treatments and cures, and could put at risk the large investments their companies intend to make in America.

Trump's idea to make Medicare pay less for some drugs, like other countries do, has been talked about a lot since he first suggested it.

That specific rule had problems, as a court stopped it from starting during President Joe Biden’s time. The companies that make medicines said that Trump's try in 2020 would let other countries have more power in choosing the cost of medicines in the U.S.

On Monday at the White House, during a long speech, Trump often supported drug companies. He said other countries were the reason why medicines cost so much for Americans. With him were Kennedy, the head of Medicare and Medicaid Services Dr. Mehmet Oz, the head of the Food and Drug Administration Dr. Marty Makary, and the head of the National Institutes of Health Jay Bhattacharya.

However, he threatened the companies with federal investigations and said he would allow more imported drugs to enter the U.S.

Trump said that drug companies make most of their money from America, and he added that he didn't think this was good.

Over the weekend, Trump talked a lot about the announcement, saying in a post that his plan could save "TRILLIONS OF DOLLARS."

However, on Monday, the White House did not provide details on how much money they expect to save.

The health department's main officials will meet with drug company leaders in the next month. They will suggest new drug prices that are based on what other countries pay, Oz said on Monday.

Rachel Sachs, a health law expert, said Americans probably won't see lower drug prices soon because of the order.

Sachs said the plan seems to be to ask companies to lower their prices on their own to a level that is not yet known. He also said that if they do not lower prices enough, the government will do other things over a long time. These actions might lower the cost of drugs in the future.

The health department can change the prices of medicines for Medicare and Medicaid by making rules, but its power is limited. In 2022, Congress passed a new law. This law lets Medicare negotiate lower prices for some prescription drugs starting in 2026. Before this law, Medicare paid the prices that drug companies asked for. Drug companies tried to stop the law in court, but they were not successful.

It is even harder for the agency to change the price of drugs for millions of Americans who have private insurance.

The U.S. regularly spends more on medicines than other big, rich countries. This problem has made both main political parties angry for a long time, but Congress has never agreed on a permanent solution.

When Trump began his first term as president, he said that drug companies were making too much money unfairly. He also complained that other countries, where governments decide how much drugs cost, were using American people unfairly.

Before the announcement, Trump used strong words against the drug industry on social media. He said that drug companies had claimed for years that Americans were the only ones paying for research and development costs.

He said that the money drug companies give to politicians to influence them "can do a lot, but not with me or the Republican Party."

"We will do what is right," he wrote.

Several drug companies saw their stock prices increase on Monday morning. For example, Merck's stock went up by 3.9%, Pfizer's by 2.5%, and Gilead Sciences' by 5.8%.