Feb 1 (Reuters) - The Biden administration is sending drugmakers opening offers for the U.S. Medicare program's first ever price negotiations on Thursday, the White House said in a statement.

President Joe Biden's signature Inflation Reduction Act (IRA) allows Medicare, which covers 66 million Americans mostly aged 65 and older, to negotiate prices for some of its most costly drugs.

The negotiations will continue over the next several months, ending by August, the U.S. Department of Health and Human Services said in a statement, and the negotiated prices are expected to go into effect in 2026.

The initial offers have been sent to manufacturers of 10 high-cost medicines, which include Bristol Myers Squibb and Pfizer's blood thinner Eliquis, Merck & Co's diabetes drug Januvia and Johnson & Johnson's blood thinner Xarelto.

The HHS and White House did not disclose details on the offers.

Five Wall Street analysts and two investors told Reuters they expect the negotiations over prices that will go into effect in 2026 to result in cuts ranging from the statutory minimum of 25% to 60% when the final numbers are set in September. (Reporting by Urvi Dugar and Sriparna Roy in Bengaluru; Editing by Toby Chopra and Sriraj Kalluvila)