About 7% of Medicare Advantage plan enrollees will have to find new plans in 2010, according to officials at the federal Centers for Medicare and Medicaid Services.

About 99.9% of all Medicare beneficiaries who have access to Medicare Advantage plans today will have access to a Medicare Advantage plan in 2010, but some of the plans are withdrawing from the market, officials say.

About 1.5% of all Medicare beneficiaries will have to choose new plans or enroll in “original Medicare” in 2010 because their plans are withdrawing from the market, officials say.

“Most of these plans are private fee-for-service plans that made their business decisions to exit the program,” officials say.

UnitedHealthcare, a unit of UnitedHealth Group Inc., Minnetonka, Minn., says the federal government has reduced funding for the Medicare Advantage program by about 5% for 2010.

America’s Health Insurance Plans, Washington, says CMS made the Medicare Advantage cuts based on an assumption that Medicare physician payments will be cut by 21%.

Everyone agrees that Congress will never let that policy take effect, AHIP President Karen Ignagni says in a statement.

“Incorporating this assumption into Medicare Advantage payment rates is resulting in higher premiums or reduced benefits for many of the 11 million seniors enrolled in Medicare Advantage,” Ignagni says.

Health policymakers who are now considering “drastic cuts to Medicare Advantage” should think about the effects those cuts will have on seniors’ premiums and benefits, Ignagni says.

When UnitedHealthcare announced its 2010 Medicare Advantage product menu today, it said it has tried to minimize the effects of the funding cut on the people who will use its Medicare products in 2010, by working to preserve popular features such as wellness and care coordination services.

UnitedHealthcare will offer a total of about 330 individual Medicare Advantage plans in 2,136 counties in 49 states.

The number of Medicare regions where UnitedHealthcare offers a zero-premium Medicare Part D prescription drug product to “auto-assigned, low-income subsidy members” will increase to 27 out of a total of 34 regions, up from 25 regions today, the company says.

CORRECTION: An earlier version of this article described the CMS announcement incorrectly.

We tweet about health reform at http://twitter.com/ReformWatch

We also have started a health reform newsletter. You can sign up for it at http://www.lifeandhealthinsurancenews.com/HCRW/Pages/default.aspx