The Trump administration is ending a key health insurance subsidy program that aimed to keep premiums for seniors’ prescription drug plans in check, claiming that it benefits corporate insurance companies, according to Centers for Medicare & Medicaid Services Administrator Mehmet Oz.

Medicare Part D – the government health insurance program’s prescription drug benefit – is used by tens of millions of older or disabled beneficiaries.

The program’s subsidies are set to expire at the end of the year, the administration announced Tuesday.

That move will likely result in higher prescription costs and increase premiums for about half of recipients, according to an administration official.