Washington ? More than 3 million seniors may have to switch their Medicare prescription plan next year, even if they’re perfectly happy with it, thanks to an attempt by the government to simplify their lives.

The policy change could turn into a hassle for seniors who hadn’t intended to switch plans during Medicare’s open enrollment season this fall.

And it risks undercutting President Barack Obama’s promise that people who like their health care plans can keep them.

A new analysis by a leading private research firm estimates that more than 3 million beneficiaries will see their current drug plan eliminated as Medicare tries to winnow down duplicative and confusing coverage, in order to offer consumers more meaningful choices. Instead of 40 or more plans in each state, beneficiaries would pick from 30 or so.

“As a result of this policy, there are going to be fewer plans offered in 2011,” said Bonnie Washington, a senior analyst with Avalere Health, which produced the study. “There is still going to be robust choice for beneficiaries, but those who have to change plans could experience some disruption and inconvenience.”

While seniors would not lose Medicare coverage, they could see changes in their premiums and copayments.

Medicare officials dismissed the Avalere estimate without offering their own number. “Anybody who is producing that kind of analysis is simply guessing,” said Jonathan Blum, deputy administrator for Medicare.