WASHINGTON — Medicare says premiums for seniors enrolled in popular private health insurance plans will dip by 1 percent on average next year.

That will bring the average monthly premium to about $35, a roughly 50-cent cut, Medicare officials said this morning.

The fate of so-called Medicare Advantage plans has been a source of concern because the new health care law cuts payments to private insurance companies. However, significant reductions are still a couple years away.

The Obama administration says the program is strong and expected to remain so.

About 11 million seniors — one-fourth of beneficiaries — are signed up in the plans, and Medicare projects enrollment to increase by 5 percent in 2011.