U.S. President Donald Trump sent letters to the chief executives of 17 major pharmaceutical companies, urging immediate action to lower the cost of prescription drugs for Americans, the White House said Thursday.

Letters were sent to top executives at Eli Lilly, Sanofi, Regeneron, Merck & Co, Johnson & Johnson, and AstraZeneca, among others. Copies of the letters were posted on Trump's Truth Social account.

The president is calling on the companies to extend most favored nation pricing to Medicaid, guarantee such pricing for new drugs, and return excess overseas revenue to American patients and taxpayers, without providing details.

Trump has given the companies until September 29 to respond with binding commitments to those terms.

"According to recent data, the prices that Americans have been paying for brand name drugs are more than three times the price other similarly developed nations pay," said White House press secretary Karoline Leavitt.

She added the administration will "deploy every tool in our arsenal" to end "abusive drug pricing practices."