President Donald Trump’s decision Thursday to end subsidy payments mandated by the Affordable Care Act (“Obamacare”), designed to lower co-payments and deductibles for low-income Americans, has been met with trepidation by U.S. bishops.

Bishop Frank J. Dewane of Venice, Florida, Chairman of the U.S. Conference of Catholic Bishops’ (USCCB) Committee on Domestic Justice and Human Development, said of ending the subsidies, “this is of grave concern.” He acknowledged the flaws of Obamacare, but warned that “as leaders attempt to address impending challenges to insurance market stability and affordability, they must not use people’s health care as leverage or as a bargaining chip.”

Trump campaigned on repealing Obamacare altogether. Yet since congress was unable to pass a bill to do so, Trump is doing what he can from the Oval Office to chip away at it. His administration has also cut Obamacare’s open enrollment period in half, and cut its advertising budget, designed to help people sign up for the health exchanges, by 90 percent.

Trump also signed an executive order allowing health insurance to be sold across state lines and with fewer benefits and protections for consumers. Dewane promised that the “USCCB will closely monitor the implementation and impacts of this executive order by the relevant administrative agencies.”

Some experts fear the cumulative effect of these moves will be a return to the days of insurance companies selling bare-bone products that cover very little, which led to fraudulent policies being sold in a race to the bottom.

“In general, robust options for people to obtain health coverage, as well as flexibility and approaches aimed at increased affordability, are important strategies in health care,” Dewane said, adding that “great care must be taken to avoid risk of additional harm to those who now receive health care coverage through exchanges formed under the Affordable Care Act.”

Sarah Kliff of Vox, a journalist who has covered the Obamacare debates, projected that under the terms of Trump’s orders, by 2018, premiums will rise by 20 percent and 25 percent by 2020. She says the move will increase the deficit, and the Congressional Budget Office estimates it will cost the government $194 billion over a decade.

The CBO also estimates there will be one million more uninsured people next year due to the orders. Dewane said such exclusion of people from coverage “strike(s) at the heart of human dignity and the fundamental right to health care. The poor and vulnerable will bear the brunt of such an approach.”

The bishop said he still holds out hope congress will act to “provide a sustainable framework for health care, providing lasting solutions for the life, conscience, immigrant access, market stability, and underlying affordability problems that remain unaddressed.”