In a post on his Truth Social platform, Trump said he would sign the executive order on Monday morning, US time, to pursue what is known as "most favoured nation" pricing or international reference pricing.
The US pays the most in the world for many prescription drugs, often nearly triple that of other developed nations.
Trump has said he wants to close that spread, but has not publicly specified how and did not provide details in his post.
"They will rise throughout the World in order to equalise and, for the first time in many years, bring FAIRNESS TO AMERICA!" he said.
"I will be instituting a MOST FAVORED NATION'S POLICY whereby the United States will pay the same price as the Nation that pays the lowest price anywhere in the World," Trump added.
Drugmakers have been expecting an order that would focus on the Medicare health insurance program, according to four drug industry lobbyists who said they had been briefed by the White House.
The drugmakers expect the order to apply to a universe of drugs beyond those currently subject to negotiation under former president Joe Biden's Inflation Reduction Act.
Because of that law, Medicare has negotiated prices for 10 drugs, with those prices due to be put in place in 2026. More medicines were set to be negotiated later in 2025.
"Government price setting in any form is bad for American patients," Alex Schriver, a spokesperson for the top US drug company lobbying group, the Pharmaceutical Research and Manufacturers of America, said in a statement when asked about Trump's planned executive order.
This is not the first time Trump has tried to tie drug prices to what other countries pay. During his first term, a court blocked a proposed international reference pricing program.
That proposal five years ago was projected by his administration to save taxpayers more than $US85 billion ($A133 billion) over seven years, cutting into US annual spending of more than $US400 billion ($A624 billion) on drugs.
