WASHINGTON (AP) — More than a dozen U.S. senators from both parties are calling on the Obama administration to broaden a Medicaid program for the nation's frailest seniors, calling it a proven alternative to pricier nursing home care as states seek to limit long-term medical costs.

In a letter released Thursday, the senators urged the Centers for Medicare and Medicaid Services to follow through on plans to loosen restrictions on the Program of All Inclusive Care for the Elderly. PACE is open to Medicaid-eligible seniors and people with disabilities who need nursing home care.

The program run by Medicaid, the state-federal health insurance program for the poor, allows seniors to stay in their own homes and receive coordinated care from a team of doctors, nurses and social workers usually at an independently operated day center. But enrollment has been modest, limited somewhat by federal regulations and a recent push by states under the Affordable Care Act to move patients into more cost-effective managed-care plans.

Currently, more than 31,000 Americans 55 or older are served by 196 PACE centers in 31 states, according to the National PACE Association. Pennsylvania has the most centers, at 32, followed by California, New York, Massachusetts, Virginia and North Carolina.

Late last year, CMS said it would propose changes to allow more flexibility in enrolling patients, but it has yet to do so. A spokesman for the agency said this week that the review was continuing.

PACE is in a unique position to help CMS achieve "its goals of better care, better health and increased cost-effectiveness," the lawmakers wrote. But they said there are regulatory and statutory barriers preventing more seniors from enrolling.

The letter was spearheaded by Sens. Tom Carper, D-Del., and Pat Toomey, R-Pa., and signed by 11 other senators.

They are asking CMS to allow PACE in a wider range of community settings, such as adult day health centers or senior centers, to increase access, especially in rural areas. The lawmakers also called for a speeded-up application process and allowing seniors to keep their own doctors, rather than using a PACE-designated physician.

Jackie Backer, 77, of Lititz, Pennsylvania, says she decided to try PACE rather than moving into a nursing home after suffering a stroke five years ago.

"It's been wonderful — it helps us be independent so we live on our own, but there's also a real camaraderie and caring from the staff. I've met many new friends," she said.

Five days a week, she is picked up from her home and taken to a center in Lancaster to be monitored by doctors and other health experts. She gets meals there and participates in social activities. The costs are all picked up by Medicaid and Medicare.

The CMS review comes as the low-income seniors and people 55 or older with disabilities make up roughly one-third of total Medicaid spending.

Nursing home care costs on average $75,000 per person a year, not including expenses charged separately to Medicare for medication, emergency services or hospital stays, according to lawmakers. States set the PACE rate on average about 14 percent less of what they would otherwise expect to spend on nursing home care.

Howard Gleckman, a senior fellow at the Washington-based Urban Institute, said while patient satisfaction and health outcomes in PACE have been strong, states haven't always been convinced that the program — typically run by smaller, not-for-profit health organizations — saves money.

Under a provision of the Affordable Care Act, roughly half the states including Florida, California and New York are contracting with more traditional, managed care companies in hopes of achieving bigger savings on long-term care; instead of states paying doctors or hospitals for each individual service they provide, they pay health insurers a fixed monthly fee for all needed services.

An August 2013 brief by the AARP Public Policy Institute cautioned that while there is no evidence so far that services have been reduced, the longer-range impact of the recent shift to managed care "is unknown and should be carefully monitored."

"The managed-care organizations will get paid a lot less, so the question is, 'if they get paid less, will they do less, or can they deliver equal or better care in a more cost-effective way?'" asked Gleckman. "We don't know yet."