U.S. Sen. Susan Collins said Sunday that she is “very concerned” about President Donald Trump’s decision to stop payments to health insurers used to hold down insurance costs for low- and middle-income Americans.

“What the president is doing is affecting the ability of vulnerable people to receive health care right now,” Collins, the senior senator from Maine, said during a Sunday morning appearance on CNN’s “State of the Union.”

Trump announced Friday that he would “immediately” halt payments to insurers, known as “ cost sharing reductions,” under the Affordable Care Act, a move hailed by many conservative groups but criticized by health care and consumer groups.

Before his Friday announcement, Trump took to Twitter to blast the payments as “subsidies” to insurers: “The Democrats ObamaCare is imploding. Massive subsidy payments to their pet insurance companies has stopped. Dems should call me to fix!”

Collins challenged the president’s characterization of the payments as a “windfall” to insurers.

“What this money is used for is to help low-income people afford their deductibles and their copays so that their health care is available to them,” the Republican senator said.

The payments made to insurers to help them hold down copayments and deductibles for low- and middle-income Americans. It will cost about $7 billion this year and help more than 6 million people, according to the Associated Press.

The National Association of Insurance Commissioners estimated that the cancellation of these payments would cause premiums to increase 12 percent to 15 percent in 2018 on top of already anticipated rate hikes.

Maine’s insurance superintendent, Eric Cioppa, in August approved double-digit rate increases, ranging from 18 percent to 27 percent, for 2018 health insurance plans on the individual market, according to a previously published report. Those rate increases were made under the assumption that the federal government would continue to make the payments to insurers. Cioppa estimated that without the payments rates could increase 20 percent to 37 percent.

The move to eliminate payments to insurers comes on the tails of a series of moves by the Trump administration to weaken the Affordable Care Act. Trump on Thursday signed an executive order to allow the sale of health insurance plans shielded from state and federal insurance requirements. And the administration announced in August that it would significantly reduce spending on advertising to get people to sign up for insurance and “navigators” who help people sign up for coverage, according to The Washington Post.

“These are certainly very disruptive moves that will result in smaller numbers of people being insured, that will make it harder for low-income people to afford their out-of-pocket costs, and destabilize insurance markets,” Collins said.

When asked on “State of the Union” about her decision not to make a run for the Blaine House in 2018, Collins said that Washington is where “I can do the most for the people of Maine and the nation” as Congress deals with a number of consequential issues, such as a hostile North Korea, tax reform and the ongoing debate over the future of the Affordable Care Act.

“This has been an unconventional presidency, and my ability to work with people on both sides of the aisle in a bipartisan manner is needed now more than ever,” she said.