WASHINGTON — The Defense Department announced Thursday it has pushed back to October the date when it will implement changes to its health care plan for active-duty service members, retirees and their families.

Previously, officials believed the Pentagon would limit the availability of TRICARE Prime, a managed-care plan similar to an HMO, outside of a 40-mile radius of a military treatment facility when it changes the program’s administrator in Western states, including Oregon, in April 2013.

The Defense Department has intended to reduce its Prime Service Areas, or PSAs, where the HMO-like plan is offered, since it last restructured its health-care support contracts in 2007, according to the Pentagon announcement.

“Since PSAs were created to ensure medical readiness of the active duty force by augmenting military treatment facilities, bidders were only required to establish PSAs around (treatment facilities) and areas affected by Base Realignment and Closure (BRAC) decisions,” the statement reads.

In Oregon, the only two military treatment facilities are Coast Guard facilities located in Astoria and North Bend, meaning thousands of beneficiaries farther inland could lose access to TRICARE Prime. Instead, beneficiaries would have to use TRICARE Standard, the basic fee-for-service plan offered by TRICARE.

But if members live less than 100 miles from a Prime Service Area and are willing to waive the requirement that TRICARE Prime be available within an hour’s drive, they can stay in the plan, said Dian Lawhon, director of TRICARE Management Activity’s beneficiary education and support division. Lawhon encouraged beneficiaries worried about losing coverage to discuss switching to TRICARE Standard with their medical provider.

This could provide benefits for both parties, as patients benefit from continuity of care and providers maintain a robust practice, she said.

The Defense Department will mail additional information to each beneficiary in about 30 days, she said. Additionally, the Pentagon is developing a web-based tool to help people determine if they are affected by the service changes and reductions.

“We really want to make sure they have plenty of time to look at their health care options,” she said.

In December, legislation introduced by Reps. Greg Walden, R-Hood River, Suzanne Bonamici, D-Beaverton, and Mark Amodei, R-Nev., that requires the Defense Department to submit a written report on the costs and impact of the TRICARE changes to Congress within 90 days was enacted as part of the Defense Reauthorization bill.

“Military retirees who served our nation in uniform deserve the very best care our nation has to offer,” Walden said in a prepared statement, adding that he is concerned about the options left to beneficiaries who lose access to TRICARE Prime. “Now that most TRICARE Prime patients will be switched to a different insurance plan, TRICARE Standard, patients aren’t assured that their current primary care physician and health providers will be part of their network. It’s up to the Pentagon to make sure that care is not interrupted for these patients.”

According to Walden’s office, TRICARE Prime is available to thousands of military retirees under age 65 along the I-5 corridor in Oregon, including about 2,500 military retirees in southern Oregon. Additionally, the Prime option is available to a small number of military retirees within 100 miles of the I-5 corridor, such as Klamath Falls, Bend and Hood River, who chose to keep their primary care provider after moving.

Military retirees over age 65 are covered by TRICARE for Life, and the upcoming changes will not affect them, Walden said.

Statewide, the changes will affect 9,009 beneficiaries, Lawhon said. The figures for neighboring California (70) and Washington state (3,270) are much lower.

Depending on how many beneficiaries decide to waive the one-hour driving limit, the Defense Department estimates it will save between $45 million and $56 million annually once the changes go into effect, she said.

Over the past five years, the number of people enrolled in TRICARE Prime has increased by 500,000, according to the 2012 Military Health System stakeholders’ report. Almost all of the new enrollees are in network care, as opposed to active-duty military on a military base or deployed overseas. Additionally, as health care costs continue to rise, more eligible beneficiaries are opting to use TRICARE rather than private health insurance, the report states.